BRUNSWICK STEAM ELECTRIC PLANT CAPE FEAR STUDIES · 2012-11-20 · Communities in the Cape Fear...

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BRUNSWICK STEAM ELECTRIC PLANT

CAPE FEAR STUDIES

INTERPRETIVE REPORT.'

JANUARY 1980

Table of Contents

IList of Tables. . . . . . . . . . . . . . . . . .

List of Figures . . . . . . . . . . . . . . . . .

1.0 Introduction . . . . . . . . . . . . . . .

1.1 The Brunswick Steam Electric Plant (BSEP)

1.2 The Cape Fear Estuary (CFE) . . . . . . . .

1.3 History of BSEP Regulatory Review . . . . .

1.4 The Major Issues . . .. . . . . . . . . .

1.4.1 Intake Issues . . . . . . . . . . . . . .

1.4.2 Summary of Results--Intake Issues .

1.4.3 Discharge Issues and Summary of Results

1.5 Organization of Report. . . . . . . . . . .

2.0 Cape Fear Studies Program . . . . . . . . .

2.1 The General Scope of the Program. . . . . .

2.2 The Program Prior to 1976 . . . . . . . . .

2.3 Research Programs Since 1976 . . . . . . .

2.3.1 Physical and Hydrological Studies . . . .

2.3.1.1 Dye Tracer Studies (Carpenter and Yonts)

2.3.1.2 Salinity and Temperature Studies (CP&L)

2.3.1.3 River Water Chemistry Studies (CP&L). .

2.3.1.4 Tidal Monitoring Study (CP&L) . . . . .

2.3.1.5 Ocean Thermal Plume Studies (CP&L). . .

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xv

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1-1

1-3

1-5

1-8

1-9

1-11

1-12

1-12

2-1

2-1

2-4

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2-5

2-5

2-5

2-6

2-6

2-6

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Table of Contents (continued)

I

II

Pag~e

2.3.2 Larval, Juvenile, and Adult Fish and Shellfish. . . . .

2.3.2.1 Ocean Larval Fish Program (CP&L)Special Dye and Larval Study (Carpenter/CP&L) . . . .

2.3.2.2 Main Stem Estuary (NCSU, LMS) . . . . . . . . . . . .

2.3.2.3 Tributary Creek and Marsh Area Studies (LMS, NCSU). .

2-6

2-6

2-7

2-11

2-13

2-14

2-15

2.3.2.4 Nekton (UNC). . . . . . . . . . . . . . . .

2.3.2.5 Plant Entrainment Studies (NCSU). . . . . .

2.3.3 Plant Impingement Studies (CP&L). . . . . . .

2.3.4 Fish Population Model (LMS)Analysis of Population Persistence Mechanisms

2.3.5 Post-1978 Studies (CP&L). . . . . . . . . . .

(LMS).. 2-15

2-16

3.0 The Brunswick Steam Electric Plant. . . . . . . . . . . . 3-1

3.1 General Description of BSEP . . . . . . . . . . . . . . . 3-1

3.1.1 Plant Location. . . . . . . . . . . . . . . . . . . . . 3-1

3.1.2 Physical Features of Plant. . . . . . . . 0 . . . . . . 3-1

3.1.3 Description of Circulating Water System . . . . . . . . 3-3

3.1.3.1 Intake Canal. . . . . . . . . . . . . . . . . . . . . 3-3

3.1.3.2 Intake Structure and Nekton Return System . . . . . . 3-4

3.1.3.3 Condensers. . . . . . . . . . . . . . . . . . . . . . 3-6

3.1.3.4 Discharge Facilities. . . . . . . . . . . . . . . . . 3-7

3.1.4 Operating History; Start-up Problems andDesign Modifications. . . . . . . . . . . . . . . . . . 3-8

3.1.5 Flow Rates. . . . . . . . . . . . . . . . . . . . . . . 3-10

3.2 Potential Cooling System Modifications. . . . . . . . . . 3-13

3.2.1 Flow Minimization ......... .... ... .. . 3-13

3.2.2 Cooling Towers . . . . . . . . . . . . . . . . . . . . 3-25

3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

ii


Page

4.0 Physical Parameters of the Cape Fear Estuary. . . . . . . 4-1

4.1 Physical Description of the Estuary . . . . . . . . . . . 4-1

4.2 Hydrodynamics of the Estuary. . . . . . . . . . . . . . . 4-3

4.2.1 Freshwater and Tidal Flows. . . . . . . . . . . . . . . 4-3

4.2.2 Interaction of Flows and the Two-layer Flow Pattern . 4-7

4.2.3 Significance of Estuary Flows . . . . . . . . . . . . . 4-11

4.2.4 Exchange or Transfer Rates. . . . . . . . . . . . . . . 4-11

4.2.5 Recirculation . . . . . . ... . . . . . . . . . . . . . 4-14

4.3 Salinity. . . . . . . . . . . . . . . . . . . . . . . . . 4-18

4.4 Temperatures. . . . . . . . . . . . . . . . . . . . . . . 4-20

4.5 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . 4-21

5.0 Use of Cape Fear Estuary by Representative Species. . . . 5-1

5.1 Representative Important Species. . . . . . . . . . . . . 5-1

5.1.1 Species and Taxa of Larvae. . . . . . . . . . . . . . . 5-2

5.1.2 Species and Taxa of Nekton. . . . . . . . . . . . . . . 5-2

5.1.3 Representative Important Species and Taxa . . . . . . . 5-2

5.2 Use of Estuary as a Nursery Area by RepresentativeImportant Taxa. . . . . . . . . . . . . . . . . . . . . . 5-5

5.2.1 The Cape Fear Estuary as a Nursery - GeneralObservations. . . . . . . . . . . . . . . . . . . . . . 5-7

5.2.2 Partitioning of Nursery Zones . . . . . . '. . . . . . . ;-10

5.2.3 Use of Estuary by Juveniles . . . . . . . . . . . . . . 5-12

iii

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Pa!

5.3 Specific Data on Use of CFE by Larvae and Postlarvae. . . 5-13

5.3.1 The Ocean (Coastal Zone) Source . . . . . . . . . . . . 5-13

5.3.1.1 Ocean (Coastal Zone) Abundance and Seasonality. 5-14

5.3.1.2 Ocean (Coastal Zone) Spatial Distribution . . . . . . 5-18

5.3.2 Larval Retention and Transport Mechanisms andDistribution of Larvae within the Estuary . . . . . . . 5-21

5.3.2.1 Intensive Transects (NCSU). . . . . . . . . . . . . . 5-24

5.3.2.2 Larval Retention Study (LES). . . . . . . . . . . . . 5-35

5.3.2.3 Abundance and Seasonality .. 5-35

5.3.2.4 Spatial Distributions .. 5-54

5.3.2.5 Summary of Evidence Concerning Residence Zones. . . . 5-70

5.3.2.6 Growth. . . . . . . . . . . . . . . . . . . . . . . . 5-88

5.3.2.7 Trends in Larval Abundance in the Cape Fear Estuary 5-90

5.4 Specific Data on Use of the CFE by Juveniles and Adults . 511'

5.4.1 Abundance, Seasonality, and Distribution. . . . . . . . 5-

5.4.2 Fluctuations in Abundance of Juveniles and Adults 5-118

5.4.2.1 Introduction. . . . . . . . . . . . ... . . . . . . . 5-118

5.4.2.2 Penaeid Shrimp. . . . . . . . . . . . . . . . . . . . 5-119

5.4.2.3 Finfish . . . . . . . . . . . . . . . . . . . . . . . 5-129

5.4.3 Recreational and Commercial Significance of CapeFear Nekton .. 5-139

6.0 Entrainment and Impingement at the Brunswick Plant. . . . 6-1

6.1 Entrainment of the Various Species Over theYearly Cycle. . . . . . . . . . . . . . . . . . . . . . . 6-2

6.1.1 Entrainment Rates . . . . . . . . . . . . . . . . . . . 6-2

6.1.2 The Areas from which Larvae are Entrained . . . . . . . 6-33

6.2 Impingement of the Various Species Over theYearly Cycle. . . . . . . . . . . . . . . . . . . . . . . 6-45

6.2.1 Impingement Rates . . . . . . . . . . . . . . . . . . . 6-4-

-6.2.2 The Area from which Juveniles are Impinged. . . . . . . 6-

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Page

6.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . .

7.0 Assessment of Conditional Plant Mortality of Spotand Croaker by the Fish Population Model. . . . . . . . .

7.1 Description of the Fish Population Model. . . . . . . . .

7.1.1 Introduction . . . . . . . . . . . . . . . . . . . . .

7.1.2 Model Development . . . . . . . . . . . . . . . . . . .

6-64

7-1

7-1

7-1

7-24

7.2 Assessment of Conditional Mortality on Spot . . . . .

7.2.1 Spot Utilization of the Cape Fear Estuary .

7.2.2 Evaluation of Input Parameters. . . . . . . . . . .

7.2.2.1 Larval Recruitment. . . . . . . . . . . . . . . .

7.2.2.2 Natural Mortality Rates . . . . . ... . . . . . .

7.2.2.3 Vertical Migration Preferences. .,; . . . . . . .

7.2.2.4 Larval Growth Rate. . . . . . . . .. . . . . . . .

7.2.2.5 Plant Entrainment and Impingement Rate. . . . . .

7.2.2.6 Net Nontidal Flows and Ocean Exchange Rate. . . .

7.2.2.7 Gear Efficiency . . . . . . . . . . . . . . . . .

7.2.3 Model Calibration with Spot Data. . . . . . . . . .

7.2.4 Conditional Mortality of Spot by Model Prediction

7.2.5 Sensitivity Analysis. . . . . . . . . . . . . . . .

7.2.5.1 Natural Mortality Rate. . . . . . . . . . . . . .

7.2.5.2 Larval Transfer Rate and Gear Efficiency. . . . .

7.2.5.3 Marsh Volumes . . . ... . . . . . . . . . . . . .

7.2.5.4 Treatment of Larval Transport to the Marshes. . .

7.2.5.5 The Aging Process . . . . . . . . . . . . . . . .

7.2.5.6 Retention in the Coastal Sector . . . . . . . . .

7.2.6 Summary of Conditional Mortality of Spot. . . . . .

7.3 Assessment of Conditional Mortality of Croaker. . . .

,. . 7-14

. . 7-14

* * 7-18

* * 7-18

,. . 7-19

,. . 7-20

. . 7-22

,. . 7-24

,. . 7-26

,. . 7-26

,. . 7-27

,. . 7-37

,. . 7-42

,. . 7-42

,. . 7-43

,. . 7-44

, , , 7-45

,, . 7-46

, . . 7-47

,. . 7-48

. . 7-50

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Page

7.3.1 Croaker Utilization of the Cape Fear Estuary. . . . . . 7-50

7.3.2 Evaluation of Input Parameters. 7-53

7.3.2.1 Larval Recruitment. . . . . . . . . . . . . . . . . . 7-53

7.3.2.2 Vertical Migration Preferences. . . . . . . . . . . . 7-54

7.3.2.3 Larval Growth Rate. . . . . . . . . . . . . . . . . . 7-54

7.3.2.4 Plant Entrainment and Impingement Rate. . . . . . . . 7-57

7.3.2.5 Gear Efficiency . . . . . . . . . . . . . . . . . . . 7-58

7.3.2.6 Natural Mortality Rate. . . . . . . . . . . . . . . . 7-59

7.3.2.7 Other Parameters. . . . . . . . . . . . . . . . . . . 7-59

7.3.3 Model Calibration with Croaker Data . . . . . . . . . . 7-59

7.3.4 Conditional Mortality of Croaker by Model Prediction. 7-65

7.3.5 Sensitivity Analyses . . . . . . . . . . . . . . . . . 7-67

7.3.5.1 Natural Mortality Rate.'. 7-67

7.3.5.2 Larval Transfer Rate and Gear Efficiency. . . . . . . 7-'-

7.3.5.3 Retention in the Coastal Sector . . . . . . . . . . . 7

7.3.6 Summary of Condit'onal Mortality of Croaker .7-70

8.0 Assessment of Plant Entrainment and Impingement Effects 8-1

8.1 Insights Regarding Environmental Impact . . . . . . . . . 8-4

8.1.1 There is no Persuasive Evidence of Abnormal Trendsin Relative Abundance of Either Larvae or Juvenilesand Adults of the Eight Representative Taxa . . . . . . 8-5

8.1.2 There is no Persuasive Evidence of the Plant'sPreventing, or Observably Changing, Migration ofLarvae and Juveniles to Preferred Upstream orDownstream Nursery Areas. . . . . . . . . . . . . . . . 8-7

8.1.3 There is no Persuasive Evidence of the Plant'sPreventing, or Observably Changing, Migration ofLarvae Into and Out of the Snows Marsh/Walden CreekMarsh Complex or Their Full Use of This Area. . . . . . 8-9

had

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Page

8.1.4 The Cape Fear Estuary Marshes are Responding to GrossEnvironmental Variables Such as Temperature andSalinity, Which are the Primary Determinants ofUltimate Population Levels and Which Override theLesser Effects of Entrainment and Impingement onSystem Productivity. Further, the Annual Losses tothe Juvenile Population Attributable to the Plant,as Shown by a Conservative Modeling Study and WithoutAssuming Any Compensation, are Less Than NaturalYear-to-Year Variability for the Species Modeled. . . . 8-10

8.1.5 The CFE Marshes are Supporting Populations VerySimilar to Comparable Marshes in Other EstuariesUninfluenced by Power Plant Withdrawals . . . . . . . . 8-13

8.1.6 There is no Persuasive Evidence of Any Changein, or Alteration of, the Structure of NektonCommunities in the Cape Fear Estuary. . . . . . . . . . 8-13

8.1.7 The Cape Fear Estuary Appears to be Operating atits Carrying Capacity with Available' RecruitsOccupying all Suitable Habitat as it BecomesAvailable-Shown in Part by the Fatv That theTotal Productivity of the CFE for ql SpeciesCombined has Remained Constant in the Face ofVariations in Abundance of Individual Speciesfrom Year to Year .... . . . . . . . . . . . . . . . 8-15

8.1.8 The Total Number of Adults of the Seven Commerciallyand Recreationally Important CFE Taxa Which Couldbe Produced by the Larvae Entrained and JuvenilesImpinged are Insignificant Environmentally andEconomically as Evaluated by or Measured Against:

* The "Open" Nature of the System

* The Large and Widely Dispersed Populations

* The "Robustness" and "Resilience" of EstuarineSystems

* Long-term Fishery Statistics

* What is Known About the Effects of the Commercialand Scrap Fishery on the Persistence of TheseSpecies

* Stock Recruitment Analysis

* The Economic Worth of Each Species if Caught andSold on the Commercial Market. . . . . . . . . . . . 8-17

vii

,Table of Contents (continued)

Paite

8.2 Insights on Risks and Consequences of UnderestimatingEnvironmental Impact . . . . . . . . . . . . . . . . . . 8-21

8.2.1 The Populations Affected are Abundant Along theAtlantic Coast. They Generally Spawn Over LargeAreas and for Extended Periods, and They Have HighFecundity, Indicating that the System CouldReadily Recover From Any Extreme Localized Impact . . . 8-23

8.2.2 The Life Span of the Species in Question isRelatively Short, Indicating that Any GreatPerturbation in Population Levels Should beDetected Quickly and that Upon Initiation ofRemedial Measures Population Levels ShouldRecover Quickly . . . . . . . . . . . . . . . . . . . . 8-23

8.2.3 The Populations Affected are All ExploitedCommercially, but With the Possible Exceptionof Menhaden, Probably Far Below the LevelsRequired Before There is Any Danger of Over-exploitation. . . . . . . . . . . . . . . . . . . . . . 8-24

8.2.4 The BSEP Does Not Threaten Rare or EndangeredSpecies or Anadromous Spec4ir . . . . . . . . . . . . . 8-25

8.2.5 A Sufficient Data Base Exists to Monitor Long-Term Trends and Observe Any Serious EnvironmentalPerturbations in Sufficient Time to Take RemedialAction, Whether it be Flow Minimization orConstruction of Cooling Towers. . . . . . . . . . . . . 8-25

8.2.6 There is no Persuasive Evidence That Populationsof Fish and Shellfish Affected by the BSEP WouldIn Fact Increase Either If Flow Minimization ata First-Year Cost of $6.2 Million or CoolingTowers at a First-Year Cost of $45.3 MillionWere Required .... . . . . . . . . . . . . . . . . . 8-26

9.0 Thermal Effects .... . . . . . . . . . . . . . . . . . 9-1

9.1 Area of Thermal Impact. . . . . . . . . . . . . . . . . 9-1

9.2 Effect of Heated Water on Fish and Shellfish. . . . . . . 9-4

viii


10.0 Glossary . . . . . . . . . . . . .a . . . . . . . . . .

- Cape Fear Estuary Studies Map.

Page

10-1

In insideback cover-pocket

ix

List of Tables

Table Page

2.2-1 Index to BSEP Cape Fear reports and time periodcovered 1968-1979 .2-4a

2.3-1 Sources and relative size of variance in larvaldensity estimates for total organisms and eightspecies computed from log transformations andexpressed as % of total . . . . . . . . . . . . . . . 2-10

3.1-1 Average monthly BSEP power level since commercialoperation (MWe net) . . . . .3-9

3.1-2 Simulated long-term flows under normal operation . . 3-14

3.2-1 Possible reduction in flow through Flow Minimization. 3-16

3.2-2 Simulated long-term flows under normal operationversus simulated long-term flows with FlowMinimization . . . . . . . . . . . . . . . . . . . . 3-17

3.2-3 Losses in maximum plant (2 units) output underrestrictions of Flow Minimization . . . . . . . . . . 3-22

3.2-4 Estimates of additional costs associated withFlow Minimization (million $) . . . . . . . . . . . . 3-23

3.2-5 Average loss in plant (2 units) capacity oncooling towers . . . . . . . . . . . . . . . . . . . 3-30

3.2-6 Estimates of additional costs associated withcooling towers and closed-cycle operation(million $) . . . . . . . . . . . . . . . . . . . . . 3-31

5.1-1 Percent of total catch of the abundant larvalspecies collected in the Cape Fear Riverestuary, 1974-1978. . . . . . . . . . . . . . . . . . 5-3

5.1-2 Percent of total catch of the top 20 nektonspecies collected in the Cape Fear Riverestuary, 1974-1978. . . . . . . . . . . . . . . . . . 5-4

5.3-1 Analysis of variance results for intensive rivertransects . . . . . . . . . . . . . . . . . . . . . . 5-25

5.3-2 Analysis of variance summary for the larvalretention program, Cape Fear estuary 1978 . . . . . . 5-37

List of Tables (continued)

Table Page

5.3-2a Duncan's multiple range comparisons of meandensities (Loglo (density +1)] of larvae andpostlarvae in different areas of the river(Channel, Shallow, and Ocean stations inAreas A, B, C, D, and Intake Canal at Surfaceand Bottom) and in the BSEP discharge sluiceway(Entrainment) . . . . . . . . . . . . . . . . . . . . 5-55

5.3-3 River density group comparisons Loglo (Density +1)Spot .. . . . . . . . . ... ... . . . . . . . . . . . 5-74Spo .57

5.3-4 River density group comparisons Loglo (Density +1)Flounder . . . . . . . . . . . . . . . . . . . . . . 5-75

5.3-5 River density group comparisons Loglo (Density +1)Menhaden .5-76

5.3-6 River density group comparisons Loglo (Density +1)Seatrout.. ... .... 5-77

5.3-7 River density group comparisons Loglo (Density +1)Shrimp . . . . . . . . . . . . . . . . . . . . . . . 5-78

5.3-8 River density group comparisons Loglo (Density +1)Anchovy . . . . . . . . . . . . . . . . . . . . . . 5-79

5.3-9 Results of quadratic model analysis on spot -

Loglo (density +1) .... . . . . . . . . . . . . . 5-82

5.3-10 Results of quadratic model analysis on croaker- Logl0 (density + 1) . . . . . . . . . . . . . . . 5-83

5.3-11 Regression analysis of trends in the abundance ofselected species of larvae at three river stationsand in entrainment .... . . . . . . . . . . . . . 5-108

5.4-1 Seasonality of juveniles (age 0) of major speciesin CFE . . . . . . . . . . . . . . . . . . . . . . . 5-114

5.4-2 Annual commercial landings (pounds) for repre-sentative important species and statewide priceper pound based on North Carolina fisherystatistics . . . . . . . . . . . . . . . . . . . . . 5-140

5.4-3 Trip numbers, sampling dates, and analysis periodsfor larvae and postlarvae entrained by the BSEP,1974-1978 . . . . . . . . . . . . . . . . . . . . . 5-145

xi

ToList L f Tables (continued)

I

Tab e Page

6.1- Minimum, maximum, and mean density (number per1000 cubic meters) of larvae entrained, 1974-1978. . 6-8

6.1- Relative abundance of anchovy larvae in theestuary generally, in Section B, and in entrain-ment samples . . . . . . . . . . . . . . . . 6-34

6.1- Relative abundance of trout larvae in theestuary generally, in Section B, and in entrain-ment samples . . . . . . . . . . . . . . . . . . . . 6-35

6.1- Relative abundance of mullet larvae in theestuary generally, in Section B, and in entrain-ment samples . . . . . . . . . . . . . . . . . . . . 6-36

6.1-5 Relative abundance of croaker larvae in theestuary generally, in Section B, and in entrain-ment samples . . . . . . . . . . . . . . . . . . . 6-37

6.1-6 Relative abundance of spot larvae in theestuary generally, in Section B, and in entrain-ment samples . 6-3;

6.1-7 Relative abundance of shrimp larvae in theestuary generally, in Section B, and in entrain-ment samples .6-39

6.1-8 Relative abundance of flounder larvae in theestuary generally, in Section B, and in entrain-ment samples .6-40

6.1-9 Relative abundance of menhaden larvae in theestuary generally, in Section B, and in entrain-ment samples .6-41

6.1-10 Comparison of average entrainment length withaverage river length by section (A, B, C, and D) . . 6-43

6.2-1 Numbers of impinged organisms in 1974 by monthand species . . . . . . . . . . . . . . . . . . . . 6-47




Table Page



6.2-6 Numbers of impinged organisms in 1979 by monthand species. ......... 6-52

7.1-1 Life-stage designations . . . . . . . . . . . . . . 7-8

7.1-2 Ranking of entrainment among eight species atBrunswick Steam Electric Plant (1974-1978) . . . . . 7-13

7.2-1 Mortality estimates for spot populations in fourmarsh systems, Cape Fear estuary . . . . . . . . . . 7-19

7.2-2 Density ratios for spot computed from the NCSUdata . . . . . . . . . . . . . . . . . . . . . . . . 7-21

7.2-3 Total numbers of spot entrained atid impinged byBSEP . . . . . . . . . . . . . . . . . . . . . . . . 7-25

7.2-4 Monthly average (cfs) flows undere projected plantoperation mode compared to flow reductionproposal . . . . . . . . . . . . . . . . . . . . . . 7-39

7.2-5 Conditional mortality of spot in 1977 and 1978 ascomputed by the Fish Population Model . . . . . . . 7-40

7.3-1 Density splits for Atlantic croaker computedfrom the NCSU data . . . . . . . . . . . . . . . . . 7-55

7.3-2 Total numbers of Atlantic croaker entrainedand impinged by BSEP .7-58

7.3-3 Conditional mortality of croaker in 1977 and 1978as computed by the Fish Population Model . . . . . . 7-66

8.1-1 Standing crop estimates of major taxa. . . . . . . . 8-14

8.1-2 Equivalent commercial value of fish lost byentrainment and impingement at BSEP during fullflow conditions. . . . . . . . . . . . . . . . . . . 8-19

8.1-3 Comparison of estimated equivalent adult lossesat BSEP to the North Carolina coastal commercialfishery. . . . . . . . . . . . . . . . . . . . . . . 8-20

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Table Page

8.1-4 Equivalent commercial value of fish lost byentrainment and impingement at BSEP under fullflow (1977-1978 average) conditions . . . . . . . . . 8-22

9.1-1 Maximum temperature difference ( 0C) between the .edge of hypothetical 60-acre area and ambient . . . . 9-3

xiv

List of Figures

Figure - Page

1.1-1 Cape Fear estuary study area . . . . . ... . . . . . 1-2

3.1-1 BSEP plot plan . . . . . . . . . . . . . . . . . . . 3-2

3.1-2 BSEP circulating water system intake structure . . . 3-5

3.2-1 Actual historical flow versus Flow Minimization . . 3-18

3.2-2 Fish diversion net location . . . . . . . . . . . . 3-20

3.2-3 Flow Minimization with peak larval abundancessuperimposed. . . ....... 3-26

4.1-1 Principal features of the Cape Fear River basin . 4-2

4.1-2 Marsh complexes with acreage/percent of totalmarsh of Cape-Fear estuary . . . . . . . . . . . . . 4-4

4.2-1 Cape Fear estuary freshwater inflow - averagemonthly flow 1952-1979 . . . . . . . . . . . . . . 4-6

4.2-2 NOAA data, nontidal net current, May-June 1976 . . . 4-9

4.2-3 Surface dye, pptr, July 28, 1977, slack after ebb. . 4-15

4.2-4 Surface dye, pptr, July 28, 1977, slack afterflood .4-17

4.3-1 Salinity gradient May 17, 1976, slack after ebb . . 4-19

4.4-1 A comparison of intake canal water temperatures,Jan. 1974 - Aug. 1978 .4-22

5.3-1 Densities of spot larvae collected during 3oceanlarval sampling, 1976-1978 (number/l000 m ) . . . . 5-16

5.3-2 Densities of anchovy larvae collected during oceanlarval sampling, 1976-1978 (number/1000 m ) . . . . 5-17

5.3-3 Spatial distribution of the dominant organismsduring periods of peak abundance in the oceanlarval sampling grid .5-22

5.3-4 Intensive river depth vs. day-night interactions . . 5-27

5.3-5 Intensive river group vs. day-night interactions . . 5-29

5.3-6 Intensive river tide direction vs. day-nightinteractions . . . . . . . . . . . . . . . . . . . . 5-30

xv

I

iI

III

II

List of Figures (continued)

Figure

5.3-7 Intensive river group vs. depth interactions .

5.3-8 Intensive river tide direction vs. depthinteractions . . . . . . . . . . . . . . . . . . . .

5.3-9 Conceptual model for a larval retention mechanismbased on response to photoperiod and time

5.3-10 24-hour mean density of spot larvae in theCape Fear River . . . . . . . . . . . . . ... . . .

5.3-11 24-hour mean density of croaker larvae in theCape Fear River ....-..............

5.3-12 24-hour mean density of flounder larvae in theCape Fear River ..................

5.3-13 24-hour mean density of menhaden larvae in theCape Fear River . . . . . . .-. . . . . . . . . . .

5.3-14 24-hour mean density of mullet larvae in theCape Fear River . . . . . . . . . . . . . . . . . .

5.3-15 24-hour mean density of shrimp larvae in theCape Fear River . . . . . . . . . . . . . . . . . .

5.3-16 24-hour mean density of anchovy larvae in theCape Fear River . . . . . . . . . . . . . . . . . .

5.3-17 24-hour mean density of seatrout larvae in theCape Fear River . . . . . . . . ... . . . . . . . .

5.3-18 Total number of individuals captured in the CapeFear estuary marshes, 1977 . . . . . . . . . . . . .

5.3-19 Total number of individuals captured in the CapeFear estuary marshes, 1978 . . . . . . . . . . . . .

5.3-20 Seasonality curves of selected species in theCape Fear estuary marshes, 1977 . . . . . . . . . .

5.3-21 Seasonality curves of selected species in theCape Fear estuary marshes, 1978 . . . . . . . . . .

5.3-22 Upstream croaker density . . . . . . . . . . . . . .

5.3-23 Upstream spot density . . . . . . . . . . . . . . .

.3-24 Upstream brown shrimp density . . . . . . . . . . .

n.3-25 Upstream pink and white shrimp density . . . . . . .

P

5-32

5-34

5-36

5-39

5-42

5-44

5-

5-46

5-47

5-49

;-51

5- 52

5-56

5-58

5-61

xvi


Figure Page

5.3-26a Density of spot (Leiostomus xanthurus) duringpeak larval recruitment . . . . . . . . . . . . . . . 5-63

5.3-26b Density of croaker (Micropogonias undulatus)during peak larval recruitment . . . . . . . . . . . 5-65

5.3-26c Density of Atlantic menhaden (Brevoortia tyrannus)during peak larval recruitment . . . . . . . . . . . 5-67

5.3-26d Density of Paralichthys spp. (flounder) duringpeak larval recruitment . . . . . . . . . . . . . . . 5-69

5.3-27 24-hour mean density of croaker by station anddepth, October 1976 vs. October 1977. . . . . . . . . 5-71

5.3-28 24-hour mean density of croaker by station anddepth, March 1977 vs. March 1978. . . . . . . . . . . 5-73

5.3-29 24-hour mean Logl0 (density + 1) of shrimp andspot in Walden Creek marsh and Area B, Cape FearRiver .... . . . . . ... ....... . . 5-80

5.3-29a Theoretical entrainment-impingement transitionfor brown shrimp (Penaeus aztecus) based on therelationship of body size to travr4ing screenmesh dimensions . . . . . . . . . . . . . . . . . . . 5-80a

5.3-30 Predicted 24-hour mean density of spot as afunction of river flow and temperature . . . . . . . 5-84

5.3-31 Predicted 24-hour mean density of croaker as afunction of river flow and temperature . . . . . . . 5-86

5.3-32 Percent length frequency of spot by group (A-E) . . . 5-89

5.3-33 24-hour mean length of larvae in the Cape FearRiver. Species - Spot . . . . . . . . . . . . . . . 5-91

5.3-34 24-hour mean length of larvae in the Cape FearRiver. Species = Croaker . . . . . . . . . . . . . . 5-92

5.3-35 General residence distribution of Cape Fearpostlarvae ..... . . . . . . . . . . . . . . . . 5-93

5.3-36 Plot of larval densities over time and distanceupstream. Species - Spot. Depth = Bottom . . . . . 5-94

5.3-37 Plot of larval densities over time and distanceupstream. Species = Spot. Depth = Surface. . . . . 5-95

5.3-38 Plot of larval densities over time-and distanceupstream. Species = Croaker. Depth = Bottom . . . . 5-96

xvii


Figure Page

5.3-39 Plot of larval densities over time and distanceupstream. Species - Croaker. 'Depth - Surface . . . 5-97

5.3-40 Plot of larval densities over time and distanceupstream. Species - Menhaden. Depth - Bottom . . . 5-98

5.3-41 Plot of larval densities over time and distanceupstream. Species - Menhaden. Depth - Surface . . 5-99

5.3-42 Plot of larval densities over time and distanceupstream. Species.- Flounder. Depth - Bottom . . 5-100

5.3-43 Plot of larval densities over time and distanceupstream. Species - Flounder. Depth - Surface . . 5-101

5.3-44 Plot of larval densities over time and distanceupstream. Species Shrimp. Depth = Bottom . . . . 5-102

5.3-45 Plot of larval densities over time and distanceupstream. Species = Shrimp. Depth -.Surface . . . 5-103

5.3-46 Plot of larval densities overtime and distanceupstream. Species a Anchovy. Depth - Bottom . . . 5-104

5.3-47 Plot of larval densities over time and distanceupstream. Species - Anchovy. Depth - Surface . . . 5-105

5.3-48 Plot of larval densities over time and distanceupstream. Species - Trout. Depth - Bottom . . . . 5-106

5.3-49 Plot of larval densities over time and distanceupstream. Species - Trout. Depth - Surface . . . . 5-107

5.3-50 Comparison of trends in river larval and entrain-ment densities . . . . . . . . . . . . . . . . . . . 5-110

5.4-1 Compilation of commercial landings and catch/effort data bases. Penaeid Shrimp . . . . . . . . . 5-122

5.4-2 Annual commercial landings and CPUE for CapeFear estuary - brown shrimp . . ... . . . . . . . 5-123'

5.4-3 Annual commercial landings - pink shrimp . . . . . . 5-126

5.4-4 Annual commercial landings and CPUE for CapeFear estuary - white shrimp . . . . . . . . . . . . -127

5.4-5 Number of days in which air temperature was lessthan 0 C . . . . . . . . . . . . . . . . . . . . ... 5-128

xvi ii

List of Figures- (continued)

Figure Page

5.4-6 Abundance fluctuations for juvenile and adultfishes in the Cape Fear estuary, 1973-1978(star drum, croaker, and pinfish). . . . . . . . . 5-131

5.4-7 Abundance fluctuations for juvenile and adultfishes in the Cape Fear estuary, 1973-1978(Atlantic menhaden, spot, and weakfish/greytrout) .5-132

5.4-8 Abundance fluctuations for juvenile and adultfishes in the Cape Fear estuary, 1973-1978(spotted hake, silver perch, and bay anchovy). . . . 5-133

5.4-9 Compilation of commercial landings and catch/effort data bases. Spot (Leiostomus xanthurus). . . 5-136

5.4-10 Compilation of commercial landings and catch/effort data bases. Croaker (Micropogoniasundulatus. . . . . . . . . . . . . . . . . . . . . . 5-138

5.4-11 Map of the Cape Fear River estuary samplingstations for 1976-1978 . . . . . . . . . . . . . . . 5-144

6.1-1 The monthly mean density of spot larvae entrained(E) compared to the density of spot larvae inSection A of the estuary (A), adjusted for gearefficiency . . . . . . . . . . . . . . . . . . . . . 6-4

6.1-2 The monthly mean density of spot larvae entrained(E) compared to the density of spot larvae inSection B of the estuary (B), adjusted for gearefficiency . . . . . . . . . . . . . . . . . . . . . 6-5

6.1-3 The monthly mean density of spot larvae entrained(E) compared to the density of spot larvae inSection C of the estuary (C), adjusted for gearefficiency . . . . . . . . . . . . . . . . . . . . . 6-6

6.1-4 The monthly mean density of spot larvae entrained(E) compared to the density of spot larvae inSection D of the estuary (D), adjusted for gearefficiency . . . . . . . . . . . . . . . . . . . . . 6-7

6.1-5 The monthly mean density of croaker larvaeentrained (E) compared to the density of croakerlarvae in Section A of the estuary (A), adjustedfor gear efficiency .6-16

xix


Figure Page

6.1-6 The monthly mean density.of croaker larvaeentrained (E) compared to the density of croakerlarvae in Section B of the estuary (B), adjustedfor gear efficiency . . . . . . . . . . . . . . . . 6-17

6.1-7 The monthly mean density of croaker larvaeentrained (E) compared to the density.of croakerlarvae in Section C of the estuary (C), adjustedfor gear-efficiency . . . . . . . . . . . . . . . . 6-18

6.1-8 The monthly mean density of croaker larvaeentrained (E) compared to the density of croakerlarvae in Section D of the estuary (D), adjustedfor gear efficiency .6-19

6.1-9 The monthly mean density of menhaden larvaeentrained (E) compared to the density of menhadenlarvae in Section A of the estuary (A), adjustedfor gear efficiency . . . . . . . . . . . . . . . . 6-21

6.1-10 The monthly mean density of menhaden larvaeentrained (E) compared to the density of menhadenlarvae in Section B of the estuary (B), adjustedfor gear efficiency . . . . . . . . . . . . . . . . 6-22

6.1-11 The monthly mean density of menhaden larvaeentrained (E) compared to the density of menhadenlarvae in Section C of the estuary (C), adjustedfor gear efficiency .6-23

6.1-12 The monthly mean density of menhaden larvaeentrained (E) compared to the density of menhadenlarvae in Section D of the estuary (D), adjustedfor gear efficiency .6-24

6.1-13 The monthly mean density of shrimp larvaeentrained (E) compared to the density of shrimplarvae in Section A of the estuary (A), adjustedfor gear efficiency . . . . . . . . . . . . . . . . 6-29

6.1-14 The monthly mean density of shrimp larvaeentrained (E) compared to the density of shrimplarvae in Section B of the estuary (B), adjustedfor gear efficiency .6-30

6.1-15 The monthly mean density of shrimp larvaeentrained (E) compared to the density of shrimplarvae in Section C of the estuary (C), adjustedfor gear efficiency . . . . . . . . . . . . . . . . 6-31

xx


Figure Page

6.1-16 The monthly mean density of shrimp larvaeentrained (E) compared to the density of shrimplarvae in Section D of the estuary (D), adjustedfor gear efficiency .... . . . . . . . . . . . . 6-32

6.1-17 Average entrainment (E) lengths versus averageriver lengths for the various estuary sections(A, B, C, and D) by species. . . . . . . . . . . . . 6-44

7.1-1 Data requirement of the Fish Population Model . . . 7-3

7.1-2 Schematization of Fish Population Model .7-5

7.1-3 Schematization of Cape Fear estuary in the FishPopulation M.odel . . . . . . . . . . . . . . . . . . 7-6

7.1-4 Conceptualization of the Cape Fear estuary adoptedin the Fish Population Model. 7-7

7.2-1 Density of spot (Leiostomus xanthurus) during peaklarval recruitment, Cape Fear area, 1977 .7-15

7.2-2 Density of spot (Leiostomus xanthurus) during peaklarval recruitment, Cape Fear area, 1978 . . . . . . 7-16

7.2-3 Mean length of spot in the combined seine androtenone collections, Cape Fear estuary marshes,1977-1978 .7-23

7.2-4 Total standing crop of spot larvae in the mainchannel, Cape Fear estuary, 1976-1977 .7-29

7.2-5 Concentration of spot larvae in the main channel,Cape Fear estuary, 1976-1977 .7-30

7.2-6 Concentration of spot larvae in selectedtributaries, Cape Fear estuary, 1976-1977 .7-31

7.2-7 Concentration of spot larvae in selected marshes,Cape Fear estuary, 1977 .7-32

7.2-8 Total standing crop of spot larvae in the mainchannel, Cape Fear estuary, 1977-1978 .7-33

7.2-9 Concentration of spot larvae in the main channel,Cape Fear estuary, 1977-1978. 7-34

7.2-10 Concentration of spot larvae in selected tributariesand the intake canal, Cape Fear estuary,1977-1978 .7-35

xxi


Figure Page

7.2-11 Concentration of spot larvae in selected marshes,Cape Fear estuary, 1977-1978 . . . . . . . . . . . . 7-36

7.3-1 Density of croaker, Micropogonias undulatus,during peak larval recruitment, Cape Fear area,1976-1977 .7-51

7.3-2 Density of croaker, Micropogonias undulatus,during peak larval recruitment, Cape Fear area,1978 . . . . . . . . . . . . . . . . . . . . . . . . 7-52

7.3-3 Concentration profile of croaker from the Tuckertrawl data .7-56

7.3-4 Total standing crop of Atlantic croaker larvaein the main channel, Cape Fear estuary, 1976-1977 . 7-61

7.3-5 Concentration of Atlantic croaker larvae in themain channel, 1976-1977 . . . . . . . . . . . . . . . 7-62

7.3-6 Total standing crop of Atlantic croaker life stages1-3 in the main channel, Cape Fear estuary,

.1977-1978 .. 7-63

7.3-7 Concentration of Atlantic croaker life stages 1-3in the main channel., Cape Fear estuary, 1977-1978 . . 7-64

8.1-1- Density at peak concentration of total fish larvaeand annual mean CPUE of total nekton in the CapeFear River estuary. . . . . . . . . . . . . . . . . . 8-16

9.1-1 Thermal patterns for BSEP ocean discharge . . . . . . 9-5

xxiii

1.0

1.1

1.2

1.3

1.4

1.4.1

1.4.2

1.4.3

1.5

In roduction

Th Brunswick Steam Electric Plant (BSEP)

Th Cape Fear Estuary (CFE)

Hi story of BSEP Regulatory Review

e Major Issues

Intake Issues

Summary of Results--Intake Issues

'Discharge Issues and Summary of Results

Organization of Report

BRUNSWICK STEAM ELECTRIC PLANTCAPE FEAR STUDIES

INTERPRETIVE REPORT

1.0 Introduction

This interpretive report summarizes the results of a decade of

biological, hydrological, and thermal studies of North Carolina's

Cape Fear estuary and of the nearshore region of the Atlantic Ocean

at the mouth of that estuary.

Using data from

these studies and from those conducted (and reported on) earlier,

MININKME111 Bill- .~ter_ a A I_! 1! V f

1.1 The Brunswick Steam Electric Plant

The Brunswick Steam Electric Plant (BSEP or Brunswick Pl4nt), owned

and operated by Carolina. Power & Light Company (CP&L),** is a large

two-unit nuclear station located adjacent to the Cape Fear estuary

near the mouth of the Cape Fear River (see Figure 1.1-1). 96M

- ~ h. elvarzct-Y)Tunits were 'p`1aced in

*As discussed on page 13, below, this interpretive report shouldbe read in conjunction with a multivolume set of comprehensive reportsentitled Brunswick Steam Electric Plant Cape Fear Studies (CFS), as wellas earlier reports and testimony regarding pre-1976 studies that arereferred to in the CFS.

**CP&L is an investor-owned public utility regulated by theNorth Carolina Utilities Commission, the South Carolina Public ServiceCommission, and the Federal Energy Regulatory Commission. CP&L servesapproximately 723,000 customers in a 30,000 square mile area whichincludes a substantial portion of the coastal plain in North Carolinaextending to the Atlantic Ocean between the Pamlico River and theSouth Carolina border, the lower piedmont section in North Carolina andSouth Carolina, and the area in and around the city of Asheville inwestern North Carolina.

1-1

I

4

| 2 34 OO

h al~ I

fgum 1.1_1. Coe Ye Darty studY anr"

1 -"

ma

Mrs.

1.2 The Cape Fear Estuary (CFE)

y (CFE),** one of a number of estuaries in North

Carolina, i er I FIRM

1oan. Th is

u-ai-UE-1.1 es. IPIR- '-- I

an I' M E I O11 MOM-I

deep - -- 4'----.:=:;t of

triw

and

of

to

.J I. UV=Mf-=WI--t £

an d Dwe~awwarLT 'r T %r s!ra renre'r 17 6 ) .-n-TTWXMC ffe3A~ ~oomac

lh.layered

fl the

port int. Net nontidal drift (described

in Section 4.2) results in a net upstream flow over a complete tidal

cycle of more saline water in the lower layer and a net seaward flow of

less saline water in the upper layer.

**Throughout this report the terms "Cape Fear estuary" and "CapeFear River" are used interchangeably. Both refer to the same waterbody although they may have slightly differing functional connotationsin the context in which used.

1-3

-4ft

i !.I91MIr � . I W.Wo

blyNEW_ I----------- I -

P -1. ! 1 i- 1. I IqWMW&e

e eis,--an"MI"I"Ir-of -the

The principal biological features of the Cape Fear estuary are determined

largely by these highly variable physical and hydrographic factors.

Ath

. IIIII

an d

*How these nursery areas are used will be explained in greater

detail in Section 5.0.

!-_

1.3 History of BSEP Regulatory Review

Th Bunwick M~a ____

and of

the 51 Ol. pe Fear

e e

pl&J~- ~ =-~ajl ~1-ml' ears.

Carolina Power & Light Company filed an application with the U. S. Atomic

Energy Commission [predecessor to the Nuclear Regulatory Commission (NRC) 3on July 31, 1968, for a permit to construct a two-unit nuclear power

plant in Brunswick County, North Carolina. Current environmental standards

were then only beginning to evolve. The first environmental issue to

surface in review of plans for the plant was the potential adverse effect

of discharging heated condenser cooling water to the Cape Fear estuary as

called for by the original plant design. With the proliferation of new

laws and regulations, additional environmental issues emerged--many of

them during reviews conducted under the National Environmental Policy

Act of 1969 (NEPA), whose scope was steadi expanding as a .esult of a

series of judicial decisions.

in. . ave

bee e r . H ee

Fedej he

Unit other regulatory

rev cts of

disch "UVv CM&

agr system

to e. The Company filed

a U. S. Army Corps of Engineers' permit application in October 1969, to

~dredge the necessary canals. Issuance of a Corps of Engineers' permit

was held in abeyance, however, until the cooling system design was

further modified to satisfy the U. S. Fish and Wildlife Service and the

Federal Water Quality Administration. Two years later, in early 1971, a

permit was finally issued pursuant to which the existing cooling system

1-5

'was constructed. wa ostutd. . - hthe

was

S ed. At that time thi Department of Interior, in which

both the Federal Water Quality Administration and the U. S. Fish and

Wildlife Service were located, wrote to the Army Corps of Engineers

enclosing a letter from the Fish and Wildlife Service which stated that:

the Applicant has included modifications (in itscooling system design] which should minimize fish

and wildlife losses in the project-affected area.

Although the Department of Interior's 1971 review of the Corps' proposed

- _ . c H - __ L ee narc under authority or NML', mhe NAM sr

tooS tf the

IiL~LL d~L~ A~t r~ U~Lr U i ~ . ____ ___..n

a ~ __ ad

a_ __ an

~- a ent to the mouth of the intake canal) of populations

S. l hencluded

th --- rring.

Ba _ in

r PA.

the

a

A two-week-long adjudicatory hearing was held in June 1976, at which the

Company presented all of the then-available data (based on the limited

plant intake pump operation to that date), which.it claimed showed that

any damage to the adult populations in the estuary would in all likeli-

hood be insignificant. from

th Fear

c t

_i _I t _to ___

co ~WAon

co llIIIS - ling

Esteem.ies

i RFa MNng

ing

al

-_ -1 I _0IAdRUGGIVAM- :111 R I "I W. 4- W i rin .g.

It - dIinistra torac 11'- . -- _~x__findin g

that --- stream cooling

that T-'Yfl (and thus

ent -system

1-7

effime. the field portion of the two- ad

Although the EPA Staff and the Regional Administrator had originally

taken the position that there was no need to review or examine the data

collected between 1976 and 1978

i | e

L .. 1 LL ndilien auI ar.i anw

1.4 The Major Issues

Two major questions are addressed in this report. The first, and by

far the more important, is the effect that withdrawal of BSEP cooling

water from the CFE has on adult populations of commercially and

recreationally important species of fish and shellfish which use the

estuary as a nursery area. The Second is the effect that discharging

heated water may have on the maintenance of a balanced, indigenous

population of shellfish, fish, and wildlife in the area of the ocean

affected by the thermal discharge.

*The Regional Administrator found in his Initial Decision (ID) andSupplement to the Initial Decision (ID Supp.) that the plant would killfrom 25-99 percent of the larval and/or juvenile organisms usingthe estuary, skewed toward 60-70 percent. Specifically, the estimatesthe Regional Administrator found reliable were: 70 percent reductionof larvae in the estuary, ID at 40 (Clark); 46-63 percent of larvaewhich would exist in the estuary in the absence of the plant, ID at40 (Young); two-thirds reduction of the juvenile population, ID at 41(Young); 66 2/3 to as high as 99 9/10 percent of larvae in the estuarywould be entrained, ID at 39-40 (National Marine Fisheries Service); 25-7,percent larval reduction is to be expected from two-unit operation, IDSupp. at 113. As will be seen in this report, the principal investigatorshave concluded that none of these estimates is supported by the field datagathered since the 1976 hearings.

i-E

1.4.1 Intake Issues

Cooling water withdrawal can have two basic. types of effects on fish

and shellfish. These are commonly referred to as "entrainment" and

"impingement." Entrainment refers to the passage of small organisms

through the plant cooling system--mostly phytoplankton, zooplankton,

eggs, and larvae and postlarvae usually up to 25-30 millimeters (about

1 inch). These organisms are in the cooling water that is withdrawn

from the estuary but are too small to be caught by the plant's protective

traveling screens as the water passes through the plant's intake

structure. Impingement, on the other hand, occurs to those organisms

-mostly juvenile or adult forms of fishes, crabs, or shrimp over 25-30

millimeters long--that are caught or "impinged" on the 3/8-inch mesh

wire of the intake structure's traveling screens.

Both entrainment and impingement can result in the death of a considerable

number of larvae, postlarvae, and juveniles of the species involved. Such

plant-induced mortality occurs as direct "cropping." Significantly,

there is no toxicity (with associated persistence or biomagnification)

or habitat destruction involved. The losses of concern mainly involve

organisms which in the adult form are very plentiful and comprise a

renewable fishery resource used by man for a variety of commercial or

recreational purposes, as opposed, for example, to being rare or

endangered species.

M s

L.fecomerfa r--M MThe

UR__ __ __ __ __ __ __ __ __ __ __ __ __ __ __

pa...n-

Plant entrainment and impingement effects are required to be elevated

for regulatory purposes under < 316(b) of the Clean Water Act. The

1-9

first question under 5 316(b) is whether the organism loss or "cropping"

caused by entrainment and impingement is at such a level as to constitute

"adverse environmental impact." (Emphasis added.) If "adverse environmental

impact" is shown, the second question that must be addressed is which, if

any, among various alternative technological means of minimizing (as

distinguished from eliminating) such impact can be justified as "best,"

weighing the costs of each alternative technology against the value to be

obtained by society from such minimization.

EPA, the responsible federal agency, has provided no clear definition of

what constitutes an "adverse environmental impact" under § 316(b). It

has, however, provided some guidance in its Development Document for

Best Technology Available for the Location, Design, Construction, and

Capacity of Cooling Water Intake Structures for Minimizing Adverse

Environmental Impact (U. S. EPA, Effluent Guidelines Division, Office of

Water and Hazardous Materials, April 1976). In Appendix B of that document,

EPA suggests that one of the steps in assessing impact is to determine

(1) the percent of damage attributable to the plant and (2) the zone of

influence or habitation of the organisms affected. It chen goes on to say:

A damage level of more than average year-to-yearvariability over the area of influence should beconsidered unreasonable and alternate technologyshould be investigated. If more than one plant ispresent in an area of influence, the totalcumulative cropping should not exceed the annualaverage variation over a minimum of three yearsfor freshwater inhabitants. A more lengthy periodmay be needed for marine habitants [page 224).

Although it does not have the same official sanction as the Development

Document passage, two EPA scientists (Schneider and Beck) at its

Naragansett Laboratory suggested in a memorandum to EPA headquarters

that the following broad guidelines be provided for measuring adverse

environmental damage:

1. If a decrease in species population from operationof a cooling water system can be "seen" against thebackground noise of sampling variability and naturalvariation, it is excessive and considered adverse.

1-i:

2. A reduction in numbers of an organism greater thanone standard deviation in the year-to-year variabilitybased on the most recent five-year me n is considered

unacceptable.*

1.4.2 Summary of Results--Intake Issues

This report, in Section 8, evaluates the significance, under the tests

noted above and other tests, of BSEP plant intake effects with the

currently operating once-through cooling system. Based on a decade of

hydrological and biological field investigations, the principal investi-

gators authoring this report conclude that adverse environmental impact.

is not occurring with full two-unit flows at Brunswick.

In the alternative, however, this report also assesses the relative

effectiveness and costs of various means of minimizing plant effects.

Specifically, the report compares (1) the costs of closed-cycle cooling

and the environmental benefits of the corresponding flow reduction to

(2) the much lower cost of minimizing normal plant flow (by a 29 percent

annual reduction and up to a 45 percent reduction during the period

of peak biological activity) and the correspondlng environmental benefits.

Closed-cycle cooling towers would cost consumers of electricity $45 million

in the first year (and, on the average, $40 million a year for 18 years).**

Theoretically, such an expenditure might annually save fish and shellfish

valued at between $50,000 and $220,000** if caught by commercial fishermen

in 1978. Flow minimization would cost $6.2 million in the first year

and theoretically save fish and shellfish valued at between $20,000 and

$80,000.**

*United States Environmental Protection Agency Memorandum fromHoward Zar to Bill Jordan dated April 26, 1976.

**First-year costs are the most accurate estimate of what consumerswill pay, since operation and maintenance costs become more speculativethe further one projects them into the future. See footnote on page 3-21in Section 3.2.1 and the discussion in Sections 3.2.1 and 3.3.3.

1-11

1.4.3 Discharge Issues and Summary of Results

Discharges of heated effluent ca4 have several types of effects on

receiving water bodies. These effects are required, in some cases, to

be evaluated for regulatory purposes under § 316(a) of the Clean Water

Act. The question under 5 316(a) is whether, notwithstanding the cooling

water discharges, the "protection and propagation of a balanced,

indigenous population of shellfish, fish and wildlife in and on the

body of water" can be assured. In Section 9.0 of this report, the

principal investigators conclude that the thermal discharges from

Brunswick are so quickly mixed with the ocean at the discharge pipes

that this test is met.

1.5 Organization of Report

This summary report of the Brunswick Steam Electric Plant Cape Fear

Studies is presented in nine sections.

Section 1.0 introduces the study program and shows how it has evolved

in response to regulatory concerns. 1

Section 2.0 describes the manner in which the program has been designed

to answer the questions posed by regulatory authorities and describes

the field investigations and methods used in gathering and analyzing

the data.

Section 3.0 describes the physical layout and operation of the Brunswick

Plant and the alternative technologies available for minimizing any

adverse environmental impact.

Section 4.0 presents the relevant physical and hydrological characteristics

of the CFE that are essential to an evaluation of the effects of operation

of the BSEP's once-through cooling system.

1-12

4.0 Physical Parameters of the Cape Fear Estuary

4.1 Physical Description of the Estuary

4.2

4.2.1

4.2.2

4.2.3

4.2.4

4.2.5

Hydrodynamics of the Estuary

Freshwater and Tidal Flows

Interaction of Flows and the Two-layer Flow Pattern

Significance of Estuary Flows

Exchange or Transfer Rates

Recirculation

4.3 Salinity

4.4 Temperatures

4.5 Conclusion

4-0

4.0 Physical Parameters of the Cape Fear Estuary

An understanding of certain physical characteristics of the Cape Fear

estuary is essential if one is to understand the movement of organisms

into and out of the estuary and the manner in which they become entrained

or avoid entrainment in the Brunswick Plant. These characteristics

include (1) the size and physical shape of the estuary, (2) the flow of

water in the estuary (estuary hydrodynamics), (3) the salinity of estuary

water, and (4) estuary temperatures.

4.1 Physical Description of the Estuary

a~jr-x-iv.Parq of North Caram igOM

A ---- e~ c.--

T of

vo ~Included in the calculation is

the Elizabeth River portion of the estuary to just east of the discharge

canal, including Dutchman's Creek and the freshwater drainage canal

parallel to the Brunswick Plant discharge canal (CFS, Vol. I, p. 20).

*This figure is lower than the volume figure used in the FishPopulation Model in Section 7.0. There are two reasons for this variation.First, the volume calculation in the model includes the "coastal sector,"an area of the ocean extending beyond the estuar , which is not includedin the volume figure used here. Second, the model calculation representsthe volume of the estuary as mean water, while the figure used hererepresents the volute at mean ' 3' water.

Figure 4.1-1 PRINCIPAL FEATURES OF THE CAPE FEAR RIVER BASIN

4-2

I

1. wwith an approximate area of 22,300 acres

(CFS, Vol. 1, p. 192 comprise one area type. The acreage of

each marsh area and the percent of the total marsh it comprises

are shown in Figure 4.1-2.

2. , with a top width of 400 to

500 feet, a volume of approximately 2.6 billion cubic feet at

mean low water (2.8 billion cubic feet at mean high water), and

a surface area of about 1,500 acres (CES, Vol. I, p. 20) comprises

a second area.

3.

containing numerous scattered

islands and tidal flats, comprise the third district area type.

These areas have a combined surface area of approximately 17,900

acres and a combined volume of approximately 6.1 billion cubic

feet at mean low water (CFS, Vol. I, p. 20).

4.2 Hydrodynamics of the Estuary

~dtheions in

e se

IssWARM- ai _ 1-M' _

s. ei sms

mtN kWin ry.

4.2.1 Freshwater and Tidal Flows

4 -

- 034/9.2

625/2.3

4j-"I fZAOLIN*A

'RAL POINT[-41

/ L-

Illw

ROCKS COMPLEX408/l .6

WALDEN CREEKSNOWS MARSH17r5/y.6

CREEK

OAK ISLIND COMPLE!jZa91/ 13.1

ACRES/ PERCENT OF TOTAL

MARSH COMPLEXES WITHACREAGE/PERCENT OF TOTAL 'aOF CAPe FEAR ESTUARY.

LS<.4TH ISLAND COMPLEX9000/40.4

Figure 4.1-2

Appendix Ap 48- 52-53). ThsthPero

the

~x A,

m .During the winter and spring of L976-77 and 1977-78 (December,

through May), the average freshwater inflow was 16,300 cfs compared to

an average flow of 13,700 cfs from December through May during the

period of record (CPS, Vol. I, Appendix A, pp. 48-49). Thus the period

of intensive study was a time of relatively normal freshwater inflow.

p A time lag of about five minutes

per mile in the upstream progression of the tidal wave results in similar

tidal stages occurring about two hours later at Wilmington than they do

at Southport (CPS, Vol. I, p. 21).

with

al

Iss

It is i.artant to recognize the strength of the tidal flows in the Cape

Fear estuary. The strength of chese currents becomes clearer when the

I i s

40

36

~28-

~24,~j0I-

o16

12

'it

0(it I I t.II

052 1953 10541195Bb19566105711050 1950 1960 19116211063 1964 1065 106611067 068 1060 1070 1071 1072 1073 19741197511

Figure 4.2-1 CAPE FEAR ESTUARY FRESHWATER INFLOW -AVERAGE MONTHLY FLOW 1952-1979.

idg

lHi

amount of water flowing out of the estuary on ebb tide is compared to

the total volume of the estuary. The average amount of water discharged

from the estuary during ebb tide is 200,000 cubic feet per second, or

approximately 200,000 acre-feet per day.* The volume of the estuary

at mean low water is approximately 8.7 billion cubic feet, or about

200,000 acre-feet. In other words, _

. A large part of this ebb tide

outflow, of course, is composed of water that entered the estuary on

the previous flood tide and ebbed out immediately after it flowed in.

Nevertheless, the tremendous volume of water ebbing out of the estuary is

a strong indication that water may move from any given location in the

estuary to any other location, or into the ocean outside the estuary,

quite rapidly.

4.2.2 Interaction of Flows and the Two-Layer Flow Pattern

The flow of freshwater from upstream and the tidal flow interact to

produce structured but complex water movements in the Cape Fear estuary.

two-layere obow~~a teraolcaino eoserve - '" *, especially

- o 't~xiy Pin, ~ te net mo-v41m - - ~- ~_ Sly

eA s he~tua-- an.m

Mo heavier

sea twart- eipwa~dw

flo _

w t As seawater moves to the surface as a result of this vertical

mixing, more ocean-derived water intrudes upstream in the lower layer.

Thus a circulation pattern is developed in which the net water movement

is downstream in the upper layer and upstream in the lower layer on a

tidally averaged basis. A National Oceanic and Atmopheric Administration

*While 200,000 cubic feet per second is actually equal to about400,000 acre-fee: per day, the figure of 200,000 acre-feet per dayused in the text takes into account the fact that water is dischargedfroT the estuary only half the time.

(NOAA) study of the currents in the ship channel along the length

of estuary to Wilmington conducted in May and June 1976 showed that

the two-layer flow was present upstream of Buoy 23,* as shown in

Figure 4.2-2.

eo t-y-e--t TM" pra ear

more

coO _-.

documented this pattern:

Hydrological studies have

IoStudies conducted by Dr. James H. Carpenter and

Woodrow L. Yonts over a period of more than 30 tidal

cycles showed that net movement of water at Buoy 19 was

not uniform across the width of the estuary. @gqqe

nel and

Sn s Marsh

and d-current

area. XIn

e was a

P low

(CFS, Vol. I, pp. 26-29).

*The 1976 NOAA study showed that in the ship channel at

Buoy 15 no net upstream motion could be observed (CFS,

Vol. I, p. 26).

oDur or

MO q e estuary

at at the

d yinflowing

s arge on the

w east side

(CFS, Vol. I, pp. 29-33).

*The location of the various buoys in the channel is shown onthe Study Program Map.

Buoy

97 327In In v onP 38 An Al fin 52I_ ___ aiU I

I I -a I b . .

1o-[-I, '

D 20i-

cl 30.

40

A_ -0 0 0

NON-TIDAL NET CURRENT. KNOTS

Figuro 4.2-2 NOAA DATA, NON-TIDAL NET CURRENT. MAY-JUNE, 1978

*Drogue studies and-a dye tracer study conducted in 1978

showed that there is a large movement of inflowing water

across the shallows east of Battery Island. Much of this

water turns and ebbs down the ship channel, which passes

west of Battery Island and provides the water for the

observed net seaward displacement in this region (CFS,

Vol. I, pp. 34, 37).

MViudf f "T"M 01

in n__ _ _ _ h l

f ~ CpS, Vol. I, p.. 33). For example, hydrological studies

in the ship channel just northeast of Buoy 19 at the mouth of the

Brunswick Plant intake canal, during a period of high freshwater inflow,

showed that the maximum tidal velocity in the upper layer of the estuary

(down to a depth of 16 feet) was about 3 feet per second (ft/s) at flood

current and about 3.7 ft/s during the ebb current. In the bottom layer

(greater than 16-foot depth) the maximum velocities were about 2 ft/s

during flood current and 1.4 ft/s for ebb current (CFS, Vol. I, p. 22).

The primary reason the two-layer flow is not the dominant motion in

the seaward reach of the Cape Fear estuary appears to be the rapid

vertical mixing of water in this area. Tidal currents in the seaward

reach are very strong, and the estuary is highly complex and irregular

in shape, with many curves in the channel and islands or spoil banks

of irregular shape along its length. When the fast-moving tidal flows

interact with irregularities-in the shape of the estuary, rapid mixing

of water occurs and the differences in density between freshwater and

-- 10

seawater, essential to the existence of a two-layer flow, are considerably

reduced because the freshwater and seawater are mixed together so quickly.

A notion of the strength of these currents can be gained from the fact

that CFS investigators have seen drogues, designed to float freely on

the surface of the water and resist toppling over, being carried below

the water surfare by the current and becoming completely submerged (CFS,

Vol. 1, p. 34). At the same time, as noted above, when freshwater inflow

is high, substantial density differences can exist in the seaward reach;

and at those times, the two-layer flow is better developed.

4.2.3 Significance of Estuary Flows

The complex movement of water in the estuary provides one means by

which larvae and other organisms are transported from the ocean to the

tributary creeks, marsh areas, and upriver nursery areas.

_ _ __ he

MDMM

ebI t . Because of the net landward displacement

in certain parts of the estuary, coupled with the larva's ability to

change position in the vertical direction in the water column and drop to

the river bottom wher cities can be very low, not

ut to

irr larvae.

and% MM RR MI

4.2.4 Exchange or Transfer Rates

For organisms that float passively and, therefore, move with the water,

such as many phytoplankton and zooplankton species, the effect of the

operation of the Brunswick cooling system is to transfer these organisms

from the estuary to the ocean in direct proportion to the rate of cooling

water flow. At the same time, the complex natural flows transfer

organisms from the estuary to the ocean. The rate at which water at

the plant intake area is exchanged was measured in five dye tracer

4-11

studies by Carpenter and Yonts in 1976-78 to provide a basis for

comparing the plant-induced transfer rate with the-natural rate.

To determine the exchange rate, the investigators continuously pumped

a measured volume of dye into the estuary and took periodic readings of

the concentration of dye in the water in various parts of the estuary

(CFS, Vol. 1, pp. 22-38). Dye concentration levels in the estuary

increased for several days and then leveled off. When the dye concen-

trations stopped increasing, an equilibrium had been reached; the amount

of dye dissolved in the water leaving the estuary to be exchanged for

new water was equal to the amount of dye being pumped into the estuary.

Since the investigators knew the rate at which the dye was being

introduced into the estuary, the exchange rate is found simply by the

ratio of the dye introduction rate to steady state or equilibrium dye

concentrations in the estuary.

EC

where:

E = exchange rate

I = dye introduction rate

C equilibrium dye concentration

The choice of the use of this "dye-tagging" technique was predicated

on the following considerations. Consider a simple situation of a

river flowing in one direction (downstream) through a channel. If the

channel had a simple shape so that the current speeds were not greatly

different across the channel or varied strongly with depth, the flow

of water through the channel (any particular reach of the river) could

be measured in terms of the current speed (feet per second) multiplied

by the channel cross-sectional area (square feet).

Next consider a reach of a river with a complicated shape with islands

and variable depths across the channel so that the current speeds are

very different across the reach and with depth. The flow could be

measured by making current measurements at many positions across the

channel and with depth and cross-sectional area to estimate the flow

4-12

-throughout the section. However, an alternate approach would be to

introduce some substance whose concentration in the river could be

readily measured at a known rate and sample downstream after the

substance had been mixed from bank to bank and top to bottom in the

river. Then the total river flow rate could be simply estimated as

the ratio of the rate of introduction of the "tagging" substance

(pounds per second) to the concentration or inventory of the substance

in the well-mixed part of the river downstream (pounds per cubic foot),

and the flow rate would be estimated in terms of cubic feet per second

of water flowing through that reach of the river, or the exchange or

renewal rate of that particular reach of the river would be said to be

so many cubic feet per second.

Considering a tidal estuary such as the Cape Fear where the currents

reverse or change directions throughout the tidal cycle and the current

speeds are variable across the estuary and with depth and where there

-are two sources of water to renew or exchange with any particular

reach of the estuary (the river and ocean sdurces), direct observations

analogous to the simple current measurements in the regular-shaped

river become problematical and the "tagging" procedure is appropriate.

The investigators found, using the "tagging" procedure, that the average

exchange rate for the Cape Fear estuary where the Brunswick Plant with-

draws water is approximately 47,000 cubic feet per second (CFS, Vol. 1,

pp. 16, 40). The exchange rate is variable but does not vary as much

as freshwater inflow does. It appears to depend more on local wind

speed and direction and the height of the tides than on the rate of

freshwater inflow. For example, the observed exchange rate was 48,000

cfs in July 1977 with a freshwater inflow of about 650 cfs, while in

April 1978 the observed exchange rate was 52,000 cfs with a freshwater

inflow of 7,800 cfs. Slowest exchange was found in May 1977 when the

wind was predominantly from the southeast and weak neap tides were

present (CFS, Vol. I, p. 30).

The operation of the Brunswick Plant cooling water system with a maximum

flow rate of approximately 2,410 cfs results in the transfer of water

' -13

and associated organisms from the estuary to the ocean. This transfer

rate may be compared with the observed natural transfer rate that was

found to average 47,000 cfs. Thus, the cooling water system operation

increases the transfer.rate by approximately 5%. Reduction in

plant-induced flow will cause a proportional reduction in this incre-

mental transfer.

Carpenter and Yonts also analyzed the rate of exchange of the waters in

Walden Creek, a tidal creek just north of the intake canal, with the

waters in the ship channel. Walden Creek was observed to exchange with

the ship channel area in a period of one to two days. The tributary

creeks of Walden Creek--Nancys Creek and Governors Creek--were found

to undergo exchange in periods of three to five days, with more rapid

exchange taking place during periods of spring tides (CFS, Vol. I, p. 16).

4.2.5 Recirculation

The extent to which water that leaves the estuary on ebb tide returns on

the ensuing flood tide depends on the degree of movement away from the

estuary mouth that is caused by currents in the offshore area.

Ocean currents. Studies have shown that an ocean current flows from east

to west just seaward of the mouth of the Cape Fear estuary, carrying away

water that ebbs out of the estuary. When dye was released into the

estuary, dye-tagged water was consistently observed to move westward

after flowing out of the estuary, as shown in Figure 4.2-3. Free-floating

drogues placed in the ocean in this area were found to drift toward the

west (CFS, Vol. I, p. 34). Current meter measurements confirmed the

conclusion that an east-to-west current exists (CFS, Vol. 1, p. 37).

Because of this current at the estuary mouth, water and passively

drifting organisms do not recirculate through the estuary to the same

extent as they otherwise could. As water leaves the estuary on ebb

tide, the ocean current carries much of it away to the west and replaces

4-14

-

t~o weg

< | CAPE FEAR ESTUARY<<| SEAWARD REACH

SURFACE DYE, PPtrJULY 28, 1977SLAC.K' AFTER EBBFigure 4.2-3

I --

HUUJD -

it with new water from the east that has not been in the estuary before.

If there were no current at the mouth of,4.Me estuary, there would be

very little to prevent water from circulating into and out of the

estuary over and over again. Carpenter and Yonts observed in their

dye tracer studies that the dye concentrations in water near the mouth

of the estuary at the end of flood tide were extremely low, even when

the water flowing out of the estuary on the previous ebb contained

very high concentrations of dye, as shown in Figures 4.2-3 and 4.2-4.

From this it can be seen that the water.flowing into the estuary on

flood tide was not the same water that flowed out on ebb.

Measurements of the recirculation. Current meter measurements and dye

samples at six positions across the estuary near the mouth at Buoy 13

were carried out to provide direct estimates of the extent of recircula-

tion. Dye was being introduced into the estuary to tag the estuarine

water so that the extent of discharge water return to the estuary could

be directly observed. The results of a study in May 1977 indicated an,

average recirculation of 45% (CFS, Vol. I, p. 31), and a study in

July and August 1977 indicated an average recirculation of 37% (CFS,

Vol. 1, p. 33). The results of a study in April 1978, during a

period of especially strong southwest winds, showed greater recircu-

lation that averaged 58%. The average recirculation shown by these

three studies near the mouth of the estuary is about 47%. However,

it should be noted that these studies were conducted during periods of

strong south-southwest winds (CFS, Vol. 1, pp. 31, 33, 37), and winds

from this direction tend to increase the recirculation rate substan-

tially.* It can be expected that the average recirculation is less than

47% or in the range of 35 to 45%.

*Winds at the Brunswick Plant have been measured since 1973, andthe wind direction that has the highest frequency is from the southwest.However, winds from the southwest quadrant (SSW-WSW) have a totalfrequency of only 33%; and thus two-thirds of the time the wind blowsfrom some other direction. A "typical" wind pattern for this sitewould have two to three days of southwest winds out of any particularperiod of six to nine days (CFS, Vol. I, p. 22).

4-16

SURFACE. DYE, pptrJULY 28, 1977SLACK AFTER FLOODFigure 4.2-4

1-I -

The significance of these observed recirculation rates in terms of larval

retention is evaluated in Section 7.0 as part of the Fish Population Model.

4.3 Salinity

Information on salinity levels in the Cape Fear estuary is important to

an understanding of marine life in the region because many species have

a preference or requirement for a particular salinity range. Survival

and growth rates for these species are likely to be substantially higher

in areas where salinity is within their preferred range. Salinity is

also important because a careful study of salinity data is one of the

means by which the direction of water currents involved in the two-

layer flow can be ascertained.

Freshwater flowing into the estuary is continuously mixing with the

seawater underneath it (vertical mixing) and with the seawater down-

stream toward the ocean (longitudinal mixing). As a result, there

is never a sharp dividing line separating freshwater and saltwater.

Instead there is a gradient, with salinity gradually increasing as one

moves from Wilmington to the ocean and from the surface of the estuary

to the bottom. This gradient is illustrated in Figure 4.3-1.

In the seaward portion of the estuary, freshwater and seawater can be

so well mixed that salinity levels increase very little, or not at all,

from the surface to the bottom (CFS, Vol. I, pp. 208-09). It is at

these times that the two-layer flow pattern is not dominant.

Salinity levels in the estuary are highly variable. They are influenced

by winds, turbulence, vertical eddies, cross currents, ship traffic, rates

of evaporation (particularly in shallow areas), and most of all by tidal

conditions and the rate of freshwater inflow.

During periods of high freshwater inflow, the salinity structure of the

estuary may vary substantially from the mouth to Snows Marsh: at the

4-18

Z a

4a -

N.It'

r

.q _

C 3

, Z

X /

Ut

0

N

0).

COO

zc aa. H±430

0

zz

Figure 4.3-1 SALINITY GRADIENT MAY 17,1976 SLACK AFTER EBB

mouth the salinity structure may be highly stratified from top to bottom,

while in the area of Snows Marsh salinity may be near zero from top to

bottom (Hobbie 1971, p. 7). the

e area

pstream

i tea. D g seaward

re flRlhaverage

Su ad 7

~ppta 74).

ase. jjM

(Bobbie 1971, pp. 23-30). 9- '-aznna_ _ _ _ _ _ a _ fi

Fear

water

in

rear

.the

'T11^SS J

1971, pp. 11-30).

4.4 Temperatures

Temperatures in the Cape Fear estuary are significant for much the same

reason that salinity levels are significant. Many species prefer a certain

temperature range and tend to move toward water within that range. In

addition, since fish and shellfish are cold-blooded organisms, their

entire life cycle is influenced by temperature, including spawning time,

distribution, growth, and the like.

Water temperatures in the estuary are strongly influenced by local climatic

patterns. The climate of Brunswick County is moderated somewhat by the

relatively stable Atlantic Ocean which tends to reduce extremes of both

high and low temperatures. However, large fluctuations do occur.

Because there are many different types of streams in the estuary, ranging

from shallow tidal creeks to the 40-foot-deep ship channel, water tempera-

tures at a given moment may vary substantially in different parts of

4-20

the estuary. More important, as one proceeds from the ocean into the

shallow tidal marsh areas, temperature variability increases; summer

maximums are higher, winter minimums are lower, and changes in temperature

become greater, more rapid, and more frequent.

Temperatures in the shallow marshes are generally highest in July and

August (around 31 C) (CFS, Vol. LK, Appendix I) and lowest in January

when some portions of the estuary have occasionally been covered with

ice. Temperatures in the ship channel have reached extremes of

320C (CFS, Vol. III, pp. 3-46) and 9 C (CES, Vol. XIVd, p. 23). Annual

surface temperatures measured from 1974 to 1978 at the intake structure

of the Brunswick Plant are shown in Figure 4.4-1.

4.5 Conclusion

The precise manner in which larvae utilize the estuary as a nursery

area is very much tied to its unique physical characteristics and the

specific interaction of such variables as freshwater flow, salinity,

and temperature. These variables can influence where particular species

congregate within the system, how they get to preferred areas, and the

strength of the year class of a species, depending on the vagaries of

nature in a given year. Just how these physical parameters and variables

interact with biological characteristics of key taxa utilizing the

Cape Fear estuary is discussed in the next section of the report.

o 35- - - . 1-

F- -r La-.

10 - -0i0

wi I- :1..

o %

0 c - -' - - - - - - I -JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

* INDICATES ONLY ONE MEASUREMENT

Figure 4.4-1 A COMPARISON OF INTAKE CANAL WATER TEMPERATURES.JAN 1974-AUG 1978. (NO MEASUREMENTS MADE IN FEBRUARY, 1977)

4-22

4-23

5.0 Use of Cape Fear Estuary by Representative Species

5.1 Representative Important Species

5.1.1 Species and Taxa of Larvae

5.1.2 Species and Taxa of Nekton

5.1.3 Representative Important Species and Taxa

5.2 Use of Estuary as a Nursery Area by Representative Important Taxa

5.2.1 The Cape Fear Estuary as a Nursery - General Observations

5.2.2 Partitioning of Nursery Zones

5.2.3 Use of Estuary by Juveniles

5.3 Specific Data on Use of CFE by Larvae and Postlarvae

5.3.1 The Ocean (Coastal Zone) Source

5.3.1.1 Ocean (Coastal Zone) Abundance and Seasonality

5.3.1.2 Ocean (Coastal Zone) Spatial Distribution

5.3.2 Larval Retention and Transport Mechanisms and Distributiohof Larvae within the Estuary

5.3.2.1 Intensive Transects (NCSU)

5.3.2.2 Larval Retention Study

5.3.2.3 Abundance and Seasonality

5.3.2.4 Spatial Distributions

5.3.2.5 Summary of Evidence Concerning Residence Zones

5.3.2.6 Growth

5.3.2.7 Trends in Larval Abundance in the Cape Fear Estuary

5.4 Specific Data on Use of the CFE by Juveniles and Adults

5.4.1 Abundance, Seasonality, and Distribution

5.4.2 Fluctuations in Abundance of Juveniles and Adults

5.4.2.1 Introduction

5.4.2.2 Penaeid Shrimp

5.4.2.3 Finfish

5.4.3 Recreational and Commercial Significance of Cape Fear Nekton

5-0

5.0 Use of Cape Fear Estuary by Representative Species

The data collected in the 1976-78 Cape.Fear Studies (see Section 2.0)

now make it possible to draw several well supported conclusions about

the way in which the most important and abundant larval and nektonic

forms of fish and shellfish utilize the Cape Fear estuary. This

section review's the most significant of these conclusions, primarily

as they pertain to the representative species identified in Section 5.1.

The distinct ways in which these organisms utilize the Cape Fear are

discussed in Section 5.2 and comparisons made between three ecological

zones within the estuary: (1) the upstream reach above Sunny Point,

(2) the lower estuary, and (3) the shallow zones of the estuary,

inclu4ing tidal salt marshes, both above and below Sunny Point. These

three areas are fundamentally different in species composition, age

structure of specific populations, and habitat use by various species.

Use of all three areas as migratory pathways, staging areas, and

residence zones for young finfish and shellfish is also explored. In

Sections 5.3 and 5.4, individual life history strategies with regard to

habitat preference, behavioral patterns, and transport mechanisms are

depicted. Discussion of these topics includes the entire life cycle

(from egg to adult) and is summarized with an analysis of long-term

(5-year) trends in population abundance.

5.1 Representative Important Species

=e

Since September 1976 they have been

collected from a variety of habitat types including the ocean, upstream

and downstream areas of the ship channel, upstream and downstream

shallows in the main stem estuary, tidal creeks, and marsh habitats.

Nekton have also been collected throughout the estuary and within the

coastal zone since the inception of the studies program in 1968.

5-l

5.1.1 Species and Taxa of Larvae I'aob5-mid-

l es

ha . Although

there are distinct seasonal patterns for each species, if the percent

of total catch over the five years is calculated by species, some notion

of the relative abundance and importance of each species can be obtained.

Consistent with this, the percent of the total larval catch of the most

abundant species or taxa is presented in Table 5.1-1. This list

includes approximately 96% of all fish collected. Note that the 8

representative species listed in Section 5.1.3 comprise over 78% of

the catch.

5.1.2 Species and Taxa of Nekton

by

riod

(CFS, Vols. XIV, XIVa-e, XV). As with larvae,

the percent catch by species gives some sense of their relative

abundance. ied

i of

t tc#tble 5.1-2). The 8 species listed in Section 5.1.3

comprise over 66.0% of the catch.

5.1.3 Representative Important Species and Taxa

From the species collected in the CFS,

yses. o t

(1 I0. Mau= _ _ __X_ en

A _____- s

MM _t IU V7TEMbS)'Us-and

. However, supplementary information for other species

is also presented to support individual conclusions and to point out

peculiarities, additional trends, and other specifics of the Cape Fear

ecosystem.

5-2

Table 5.1-1 Percent of total catch of the abundant larval speciescollected in the Cape Fear River estuary; 1974-1978.

SPECIES PERCENTAGE

*AnchoaGobiosoma

LeiostomusPenaeus*

HicropogotAtherinidaCynoscionIBrevoortiaBairdiellaGobionellt

anchoviesgobies

* (naked, seaboard)I spot

shrimp* white, brown, pink)

Lias croakerLa silversides** trout

menhadenL silver perchLS gobies

(darter, sharptail,freshwater)

is green goby* pinfish

iys floundermullet

50.2

14.97.5

2.910.5.81.74.4.9

.4

.4

.7

.9

.1

78.2

96.3

IMicrogobitLagodonParalichtlMugil*

Representative Species Subtotal

Combined Total

Representative Species

5-3

Table 5.1-2 Percent of total catch of the top 20 nekton speciescollected in the Cape Fear River estuary, 1974-1978.

SPECIES

Sff VMrp (white,pink, brown 1 , 2

B l,3G 1e

TonguefishWindowpaneFringed flounderBluefishBanded drumSouthern kingfishButterfishSouthern flounder1 'Bighead searobin

NUMBER PERCMT

487,767359,487327, 194310,845

108,25687, 10375,73374,66862,86726,39923,16718,18017,32714,58214,35012,2128,3377,9*76,5225,990

22.9816.9414.6515.42

5.104.103.573.522.961.241.090.860.820.690.680.580.390.370.310.28

3

Total Catch

Rep. Species Subtotal

1Representative Species

96.55

66.13

2Pink, white, and brownmacroinvertebrate data.

shrimp catch has been included from

30ther species in these genera are included in text in theirrespective representative species groups (e.g., trout as a represen-tative species includes spotted seatrout as well as grey trout).

From CFS, Vol. XV, Table 20

5-4

There are three primary criteria which support selection of these

species for more detailed study and analysis. First, as can be'seen

from Tables 5.1-1 and 5.1-2, they roughly account for 78% and 66.0%,

respectively, of the larvae and nekton captured in the estuary. Second,

they are species and taxa used by man for commercial or recreational

purposes. The only exception is the anchovies, which are considered

to be an important forage group. Third, the eight selected taxa

encompass the major life history strategies identified in the CFS. For

example, spot young arrive in the estuary during winter, migrate to the

marshes, and remain there for several months before leaving the marshes

and eventually moving offshore to overwinter. Brown shrimp appear to

use the estuary in a similar fashion but on a slightly different time

scale. Another pattern is exemplified by croaker which migrate to the

estuary during winter, move to upstream areas where they remain for

several months using the deeper tidal creeks and main stem areas, and

finally move down the estuary and eventually offshore to overwinter.

Anchovies represent another strategy since they complete their life

history within the confines of the estuary or nearshore areas of the

ocean. Taken together, these species present a rather comilete picture

of estuary utilization. No populations of rare or endangered species

are threatened by the plant, nor is there any anadromous or catadromous

species which the BSEP could realistically be presumed to be affecting.

5.2 Use of Estuary as a Nursery Area byRepresentative Important Taxa

Estuaries consist of readily identifiable habitats and characteristic

life zones: marshes, tidal flats, sounds, bays, and channels. The

spatial distribution of many estuarine organisms can be correlated with

physicochemical variables such as nutrient levels, salinity, temperature,

and turbidity as they change along the axis of the estuary (Remane 1934,

Khlebovich 1967, Boesch 1977). From an ecological standpoint, some

estuarine organisms tend to use a narrow range of habitats, or are

The top 20 nekton species by total catch do not include all 8 ofthe representative species. The percentage is derived frcm CFS, Vol. XV,Tables 8 and 20.

5 -5

limited to a narrow portion of the environmental gradient. Other

species, however, move freely between habitats and can tolerate a wide**

range of environmental conditions.

Estuaries may be viewed as rigorous environments where the fauna

living within them are subjected to wide extremes in temperature, .

salinity, and other variables. Despite their putative "harshness,"

however, many estuaries support a surprisingly rich and varied fauna

(although not comparable to, e.g., coral reefs or tropical rain forests)

and are usually associated with high levels of productivity.

An important function of estuaries is the extent to which they serve

as nursery grounds for a wide variety of marine (and estuarine) spawned

fishes and shellfishes, including those of commercial and recreational

importance. McHugh (1967) has estimated that over 80-90% of the

commercial and recreational fisheries catches along the Atlantic and

Gulf coasts of the United States involve species with estuarine-

dependent life stages. Usually, estuaries serve as nursery grounds

for these species during their first year of life. Purvis (1976),..

studying Pamlico Sound, has recognized three estuarine zones associated

with different life stages and the spatio-temporal sequence of nursery

utilization. The smallest individuals of several species were found

most commonly in shallow, brackish water zones on the periphery of the

estuary, including tidal marshes and shallow, muddy, vegetated areas.

These habitats were defined by Purvis as primary nurseries. With

increasing size, these organisms gradually moved downstream (or down

estuary) into larger creeks and bays and finally as late juveniles

they frequented open waters of the sound. Similar patterns have been

observed in the Cape Fear estuary and in many other estuaries from

the Chesapeake Bay (Haven 1957) to the Gulf states (Herke 1971,

Parker 1971).

E-g., stenohaline species are restricted to a small portion ofthe salinity gradient.

**E-g., euryhaline species are able to tolerate a wide range of

salinities.

5-6

- - -

5.2.1 The Cape Fear Estuary as a Nursery - General Observations

The nekton (swimming organisms) utilizing the Cape Fear estuary generally

fall into two categories. Certain members of the estuarine community

reside for all or most of their lifetime in the estuary; these are the

estuarine endemics or permanent residents. Most of these species,

such as killifish, silverside, and anchovies, are forage species. The

*.

It has long been recognized that the Cape Fear estuary is a "nursery"area for ocean spawned organisms such as spot, croaker, and shrimp. Justwhat this means and how the BSEP affects the Cape Fear nursery area hasbeen less clear. At one time it was postulated by scientists for variousgovernment agencies that Walden Creek, which is intersected by the intakecanal, was perhaps the most important nursery area in the estuary andthat it would be virtually depleted of organisms when the plant beganwithdrawing cooling water. As a result, it was theorized that the fishpopulations in the estuary would be reduced dramatically. Later, inreviews conducted after Carolina Power & Light Company appealed the NPDESPermit which required it to build cooling towers, several agency scientistsadvanced the theory that larvae enter the Cape Fear and once there arecirculated throughout the entire estuary at random. The BSEP withdrawswater constantly and, over time, therefore, 'most (probably 66-75 percentand possibly up to 99 percent (see footnote, page 1.8, above)) of thelarvae from the entire estuary would be drawn through the plant. Para-doxically, under this theory there are seemingly no special "nursery"areas, such as Walden Creek, to which larvae go for protection and growth.

Yet another theory, advanced by some of the scientists conductingthe Cape Fear Studies, was that larvae in the surface waters in theregion of the estuary from which the plant withdraws water were almostall lost from the estuary because the tidal currents in that area arevery strong. The water in the lower Cape Fear where the plant intake islocated is exchanged with ocean water daily, and after leaving theestuary it flows along the coast, carrying with it the larvae which werepresent in the lower portion of the estuary. As a result, pursuant tothis theory, the BSEP only entrains larvae which would have been flushedfrom the estuary and died anyway. The larvae which produce adults arethose in the "nurseries," which were theorized to be the marshes andtidal creeks. These areas, including Walden Creek, are safe from planteffects. According to the theory, larvae reach nurseries in the lowerCape Fear without passing the plant and reach upriver nursery areasby being transported in deep water in the ship channel (where there isnet nontidal flow upriver). The plant does not withdraw this water.

As a result of analysis of the data gathered in the 1976-1978phase of the Cape Fear Studies, it is now clear that none of thesetheories are totally accurate. Walden Creek supports a healthy andabundant larval and juvenile population in spite of 3SEP full poweroperation. As for the other two theories, there appears to be somezruth in each, but neicher cells the whole story.

D-/

THIS PAGE INTENTIONALLY LEFT BLANK. v

second group resides in the estuary primarily as very young (immature).

individuals and will only periodically reappear in the estuary as

adults (mainly to feed). With regard to BSEP operation, these "transient"

forms include most of the species of concern including recreational

and commercial species. They are often the numerically dominant taxa

in the nurseries; e.g., in the marshes they may constitute up to 70%

of the nekton on a seasonal basis. As adults, most of the Cape Fear

transient species spawn in the ocean, sometimes well offshore on the

continental shelf, and their young (larvae and postlarvae) are recruited

to the CFE at various times of the year. In addition, the spawning

season for these species may be rather extended (eSg., croaker spawn

from September to April) or may occur over only a 2-3 month time frame

(e.g., postlarval brown shrimp enter the estuary from February to April).

'In the South Atlantic Bight, a geographical area which encompasses the

Cape Fear estuary, r

as Meies.

A o I M-s and

n stuary.,g cond

pearing,

co- M er,

VNE

es il.

Species spawned in the ocean face the task of reaching the mouth of the

estuary and then migrating to primary nursery zones. During the oceanic

phase of migration, the swimming ability of the larvae is limited and

transport inshore occurs primarily through wind action and current

patterns. Additionally, natural mortality is believed to be very high

during this period, and consequently survivors of the inshore migration

reaching the CFE and other estuaries constitute only a small fraction

of the eggs spawned in the ocean. It is noteworthy that the CFE is an

open system" with regard to the origin of recruits. That is, many

individuals arriving at the mouth of the estuary probably do not

originate from spawning Cape Fear populations. The migratory phase for

these young organisms continues inside the estuary until a suitable,

species-specific, nursery zone is encountered. Once in these species-

specific nursery zones, residence is established with the likelihood of

increased individual survival.

Our current perception of the principles governing nursery utilization

in the CFE results from a compilation of quantitative and observational

data and includes both physical (hydrographic) and ecological

considerations. As a direct outgrowth of the Cape Fear Studies, the

lower reach of the CFE main stem, between Sunny Point (see Study Program

Map) and the ocean entrance, has become viewed as a very turbulent,

high-energy zone (CFS, Vol. I). Although some accumulation of larvae

and postlarvae takes place in this region, it is primarily a "staging

area" and it is not believed that the open waters of the lower estuary

act as an important nursery for very many species (as suggested by Purvis

1976). Functionally, this section of the estuary may perform as an

extension of the ocean itself, or as part of the "coastal zone" alluded

to in the 1976 BSEP hearings. Migration through this reach to the

primary nurseries, principally upstream, and into the extensive CFE

marshes, seems to occur in a relatively simple fashion (hydrodynamically)

although it is a direct result of rather complex behavioral patterns

exhibited by larvae and postlarvae. In other words, these young

organisms do not appear to be entirely at the mercy of tidal flows and

exchange rates in the CFE, but are able to respond to certain hydro-

graphic features of the system to avoid net seaward transport. The

ability of these tiny organisms to circumvent complete flushing from the

system is hardly surprising, in view of their rapid rates of accumu-

lation throughout the CFE, and is an expected consequence of forces of

natural selection which act to increase the organisms' chances of

survival. In this regard, note that several different behavioral

strategies have evolved in these organisms which result in their

concentration in different portions of the CFE as residence zones.

Bousfield (1955) has summarized the various components of the retention

mechanism as including:

5-9

1) changing diel vertical distributions; 2) utilization-ofthe residual, or nontidal, drift seaward in the upper layerand landward- in the bottom; and 3) changing behavioral parameterswith respect to tidal direction (see also Hughes 1969 a,b,1972; Turgeon 1976).

Individual species may utilize one or more of these mechanisms to stay

within a preferred zone of the estuary, from its mouth (Carriker 1951)

to the headwaters (Haven 1957; Turgeon 1976; Sandifer 1976).

In contemplating the retention of bivalve larvae (primarily oysters)

within the James River estuary, Wood and Hargis (1971) also emphasized

an active component for the retention mechanism, stating: ."The point

at issue is not whether such retention occurs but whether evolved

patterns of larval behavior contribute significantly to the process."

Thus, whatever the precise mechanism, larvae and postlarvae tend to

partition the CEE into several residence zones and use different

behavioral mechanisms to achieve this end. Although some overlap within

these areas occurs, centers of abundance for several taxa are clearly

associated with a specific habitat. Moreover, distributions within

each zone are not necessarily homogeneous but may be governed by

physiological tolerances, microhabitat preferences or may result from

biotic interactions such as competition and predation.

5.2.2 Partitioning of Nursery Zones

Four "niche"-related factors seem to be particularly important in

separating related species within the CFE. These factors include

temperature, bathymetric (depth), salinity (freshwater flow), and

temporal (time) components. The outcome of such separation may be a

more complete utilization of available resources such as food and

space, and, therefore, a conceivably higher survival rate for otherwise

potentially competing species. It is not clear what role biotic

interactions play as selective agents in this process, nor how they

might (or might not) interact with the abiotic components described

above. The end result, nonetheless, is clear. The CFE may be

partitioned into three distinct ecological areas:

; - I D

(1) Deep water of higher salinity in the turbulent lower reach

of the estuary.

(2) Deep water of the channel and channel slope near the head

of the estuary.

(3) Shallow areas including marshes and associated habitats -

oyster reefs, mud flats, etc.

Seasonal use in the form of sequential waves of recruitment is an added

component of this process of separation and it is frequently observed

that blosely related species use the estuary at different times of the

year. This is clearly not the result of a haphazard array of species

occurring randomly in space and time in the estuary, but rather it is

indicative of long-term evolutionary processes.

In addition to distribution among various habitats throughout the

estuary, selective distribution within habitats has also been

frequently shown to occur. Thus, the faunal composition within each

of the marshes is not, for example, necessarily homogeneous, as-.shown

by the fact that microhabitat differences occur in marshes; moreover,

they may be divided into the high marshes and tidal creeks, the latter

characterized by soft muds at their headwaters and by more scoured areas

downstream. Several properties of the water column also vary in these

creeks, being generally more stable near the creek mouth (Eackney et al.

1976), and the presence of food organisms is often correlated with

sediment properties so that predators may frequent one area more than

another (de Sylva 1975). On the basis of individual tolerances, some

species will frequent microhabitats over a wide range of conditions,

while others will be more restricted in their distribution. Importantly,

these tolerances may change with the age of the individual so that a

given species may be a member of several different communities during

its lifetime.

A consistent observation during the Cape Fear Studies has been the

dense concentrations of marine-spawned postlarvae which occur seasonally

in the upper reaches of tidal creeks and rivulets. Postlarval spot,

mullet, flounder, red drum, and other species are present in great

5-Il

5.3.2.1 Intensive Transects (NCSU)

Light - During the day larvae were not found at the surface in any great

numbers, even though there were usually higher concentrations of larvae

at the bottom. At night relatively high densities of larvae were

present at both the surface and bottom, resulting in high mean densities

relative to the daytime mean densities. This is believed to result from

daytime net avoidance and bottom-seeking behavior (larvae may be more

difficult to catch in plankton nets at the bottom of the water column).

The ANOVA tests support the conclusion that the interaction of depth by

day/night was highly significant (0.01 probability) in all but one

instance and, in that case (anchovies), it was significant at the 0.05

level (Table 5.3-1).

The depth-by-day/night interaction is complex and exhibits a slightly

different pattern for each species (CFS, Vol. VII). Spot, flounder,

and brown shrimp (which migrated all the way to the surface at night)

displayed mean surface and bottom densities at'night that were similar.

Croaker and trout showed a slightly different pattern because they did

not migrate to the surface in large numbers at any time during the

transect studies. Thus they never appeared to be evenly distributed

throughout the water column. However, the mean densities of croaker

and trout at the surface did increase sufficiently at night to cause

significant depth-by-day/night interactions (Figure 5.3-4).

Menhaden showed another slight variation of the basic pattern, but were

only present in large enough numbers to analyze in March. They were

the only finfish whose densities were highest at the surface at night

as opposed to being highest at the bottom during either day or night.

White and pink shrimp were the only species whose nighttime densities

at the bottom were considerably lower than nighttime densities at the

surface (Figure 5.3-4).

i

Table 5.3-1 and subsequent text are based on substantialstatistical analysis, much too voluminous to include in its entiretyrhere or in CFS, Vol. VII. It is available -cr inflection, however.

**March 1977 catches were brown shrimp. June 1977 were mostly

white and pink shrimp.

Table 53-4. Analysis of variance rasults for intensive dver tmauacu. -

Trip 1 (Feb ..1977) Spot Croaker Henhaden Flounder Total FishGroup **

Duccan's MR C B A C A B A B C B C A C B ADepth ** ** ** ** **Duncan's MR B>S B>S S>B B>S B>S

Gr*Dep ** * NS NS NSSta ** ** NS ** NSDay-Nite ** ** ** ** **Duscan's MR N>D N>D N>D N>D N>D

Gr*D-N ** NS ** ** **Dep*D-N ** ** ** ** **Tide-Dir NS ** NS **NS

Duncac's MR out>Vi in>outGr*T-D NS NS ** * NSDep*S-D uS NS ** NS *Tide-Lev * * ** * *Dican's MR LH LM HE M L H

Gr*T-L * NS * NS NSDep*T-L ** NS * NS **D-N*T-D NS * ** NS NSDNK*T-L NS NS * ** NS

1 1.967 1.085 0.759 0.801 2.346S .617 .549 .525 .553 .530

Trip 2(Mar..1977) Spot Croaker Menhaden Flounder Shrimp Total FishGroup NS ** * NS N* NS

Duncan's MR B A C C A B A C B A B CDepth S** N ** ** **Duncan's MR B>S B>S B>S B>S B>S

Gr*Dep ** ** NS * ** **Sta * ** ** * ** **Day-Nite ** ** ** ** ** **

Duncan's MR N>D N>D N>D N>D I>D N>DGr*D-N NS ** ** NS ** NSDep*D-N ** ** ** ** ** **Tide-Dir * ** NS ** ** NS

Duncan's MR out>in out>in in>out out>inGr*T-D NS ** ** NS ** **Dep*T-D * ** ** ** NS **Tide-Lev ** ** * ** ** **

Duncan's MR H M L H M L H M L H M L H M L H X LGr*T-L ** IS NS **Dep*T-L NS NS ** NS ** **D-*T-D** * ** ** NS **D-N*T-L uS KS ** KS ** NS

X 1.800 1.255 1.456 0.679 1.073 2.379S .539 .668 .687 .581 .534 .510

[From CFS, VoL VIl, Table 6.2]

5-25

Table 5.3.1 (Contdnued)

Trip 3 (June,1977) Trout.Group **

Duncan's MR C B ADepth **

Duncan's MR B>SGr*Dep *Sta *Day-Nite **

Duacan' s MR N>DGr*D-N **Dep*D-N **Tide-Dir NS

Duncan 's MRGr*T-D **Dep*T-D NSTide-Lav **

Duncan's .YR L MXGr*T-L NSDep*T-L MSD-N*T-D **D<N*T-L **

Anchovy**

A B CABC**

B>S**

**

**

N>D*

*

NS

NSNS**

IM H L*i-**

NS*

**

2.893.546

.

Shrid**

A B C

B>S**

N'S

*N**

N>D

**

**

**

in'out**

MSM LS

MS**

*

Total Fish**

A B C***

B>S**

*

**

N>DNS**

NS

MS*

**

IM H L**

NSNS**

SS

1.025.564

0.877.-673

3.064.435.

Trip 4(Mar. 1978)DepthDuncan's MR

StaDay-Nite

Duncan's MRDep*D-NTide-Dir

Duncan's MRDep*DirTide-Lev

Duncan's MRDep*LevD-N*T-DD-N*T-L

XS

Spot**

B>S**

**

N>D**

**

out>in**

**

E L MNSMSNS

2.100.577

Croaker**

B>S**

**

N>D**

**

out>in**

*

NS. NS

NS

1.894.592

Menhaden**

S>B**

*

N>D**

MS

NS**

H '

NSISIS

0.911.545

Flounder**

B'SMS**

N>D**

**

in>out

NSH M L

MS**

NS

1.066.509

Total Fish**

B>S**

**

N>D**

**

out>in**

**

H L M

NSMSNS

2.573.450

** 0.01 probability* 0.05 probability

[From CFS, Vol. VII, Table 6.21

5- 26

Figure 5,34 Intentive river depth VL day nigbt interactions.

MENHADEN

MAR 771*

2.0'

15.

._S B

FEB 77*0

CROAKER

MAR77 MAR 73

a b: /

ANCHOVY

JUN 7740.

3-

N'

3.0-

2.5-

I.-

0

0.a

/

2.0 Fin 770*

1.5-

1.0-

ROUNDERMAR 77

0*

MAR 780**.

1I.

1.10

TROUTJUN 77

0*N

N 0°

.5-

ft

a

5.

0� . - -

i 5 i i S 5 S

0*' (.01 PROSABSLITTY* N t.oSoSILIM

Nl-NIGHTC - CA

S ' SUtFACI* 507TOM

[From CFS, Vol. VII, Figure 6.1]

5-27

The ability of some larvae and postlarvae to control their position

in the estuary and reach or stay in preferred areas is partly

demonstrated by the interactions of day/night with group (position

in estuary Areas A, B, C, or D; see Study Program Map) and with

the tide direction. For spot, croaker, and flounders, three taxa

that were relatively abundant during the transect studies in 1977,

group by day/night interactions were significant in February 1977

for spot and flounders and in March for croaker (Figure 5.3-5).

These interactions for all three species occurred when each species

was concentrating in upstream Area "C." Differences between day and

night densities during those times were larger in the upstream areas

than in the downstream areas. Conversely, significant group-by-day/night

interactions did not occur when upstream concentrations were weak or

nonexistent (Figure 5.3-5). The differences between day and night

densities on those occasions were similar in all transects.

The ability of larvae to control their position in the estuary is

further demonstrated by day/night-by-tide direction interactions

which were generally significant on those intensive trips when

group-by-day/night interactions were not significant (Table 5.3-1).

For example, spot densities on in- and outgoing tides during February

1977 were very similar during both night and day. During March 1977,

however, a period of high river flow when spot would be moving down-

stream, nighttime densities were higher on the outgoing tide than on

the incoming tide (Figure 5.3-6). The pattern for croaker was not

quite as strong, probably because of lower densities.

Depth - Depth also played an important role in the distribution of

larvae and of postlarvae in the CFE. For most species the bottom

densities were greater than the surface densities, although menhaden;

a pelagic species, had greater concentrations at the surface than at

the bottom during February 1977. This situation was reversed in

March 1977. In all but one case (menhaden, March 1977), the

differences between surface and bottom densities were highly

significant (Table ;.3-').

5-28

Figure S6..% Imrumive river gtoup vs. daynilght Intoractior4. - '

.i

**-4.01 POAlILITYTJ A-GROUP A W-NIGHT.* -. OSIROu.AtSUTT I-GROUP a 0-OAY

NS -NOT StGNIFICANT COCCOUP C

SPOT

4* FEB 77. MAR 77'** NS

3.

2- NTM N-N-- 4

I

a 0

4,

3.

2.

1 *

CROAKER

FEB 77 MAR 77

N *N

MN

0-0., I

I~~ U

A B C A a C A h C A 8 C

4.-

za

0

00

4'

3.

*1'

fLOUNDER

FEB7 7 MAR 77us

4,

3.

2-

I.

MEWHADCNFEB 77 , MAR 77

NN

-N ° -4~

I*0

t4-w----

0 . ---- @

n- A i A * C A�. ,_ ..

.

A-- -- .

C A B C

4

TROUT ANCHOVY4 JUN77 4. JUN 77 7

4*4

3 3

2 * 20- l

A- " A 8

O- . i O __T c- , IA C A a C

4-

3.

2n

I.

SHRIMP

MAR 77 JUN 77* 1

N-_

.

cta O->N

V' . _-

A a C F UA t

(From CFS, Vol. VII, Figure 6.21

5-29

Figure 5.34. f1neralve river id. d1recdon vs. day-night tnteractions. I . ., . . . .

**- .o1p*oUAs1LI1TI I-INCOMING tool N*NIGHT* *CSPIOSAIILITY)l O-OUTGOI tt1109 3-OAY

MS I NOT SIGNWFCANT

4.

3.

2-

11-

SFEB 77

Ns

POTMAR 77 4-

2-

FEB 77

CROAKER

ItN

-0 D

3F

MAR 77

9----44o

o . . ^ _

i 0 , , 0 I. I 0

FEB n_ 4j

I

a 2-

0

2 '

FLOUNDER

IN 1 MAR n 41

31

_" 1

MENHADENFEB 77 MAR 77

****

N- N

.N-.

- a

N--- "m

i _nW . r

vr- i 0 c 0 I ' 0 i

I3

2-

1-

SHRIMPMAR 77

NS

N- N

D: O D

JUN 77

4-__ _ a4

*4

U . . ,

i 0 i 0

(From CFS, Vol. VIl, Figure 6.31

5-30

For most of the species there was also considerably significant

interaction of depth with the other primary variables in the model ---

(Table 5.3-1). Depth interacted significantly with group in many

cases and sometimes with tide direction. For example, group-by-depth

interactions were rather consistently significant for bottom-oriented

species such as spot, croaker, and trout (Table 5.3-1). For these

species, bottom densities during intensive transect studies were

consistently higher than surface densities, but the significant

interactions occurred because the difference between surface and

bottom densities generally was greater in the upstream transect than

in the downstream transect (Figure 5.3-7). This occurred because

surface densities did not increase much in the upstream areas, or in

some cases they even decreased; whereas bottom densities did increase

in the upstream areas. Other species displayed variations on this

theme, ranging from the small depth-by-group interactions for flounder

to a reversal of the usual pattern for anchovies. In their case,

bottom densities in the upstream area (Group C) were less than surface

densities, whereas the opposite was true atl the downstream transects

(Figure 5.3-7).

The significant group-by-depth interaction generally serves to illus-

trate that for many bottom-oriented species, at least, the ability to

concentrate in the upstream nursery areas is enhanced because the

organisms spend more time near the bottom in the area of net upstream

tidal drift than they do near the surface with its net downstream

movement. Menhaden, however, are somewhat different in this regard.

Although they are known to concentrate in upstream nursery areas,

factors other than depth might be more important in determining their

ability to concentrate there, since their densities during the intensive

studies were very similar at surface and bottom. It may also be that,

although menhaden were being recruited into the estuary during the

transect studies, they were not being concentrated in the upstream

area due to other environmental factors such as, for example, river

flow. They were, however, in the upstream shallow areas at this time

(CFS, Vol. IX).

5-31

FAgure 5.3.7. Intensive nyv group Yr. depth interactions..

**-`.0ol Pt3ASILITYl A-CROU A S-SURFACS* *g03PIOBSASILITY1 a-3OROJPa I-1OTOM

Ns - NOT .AGNISICANT C -Ga0wP C

SPOT4 FIB77 MAR 77

** **3-

2~~ . .&s

I- -s1 I

nl

4,

3'

2.

1 *

CROAKERFES 77 1 MAR 77

**F

8--'s .. as

n _-

V _, . . .. __

A - C A B C A B C A B C

4'

I.-3-z

22'a 1

0 10

-a

FLOUNDERF1377

NS

MAR 77MENHAD04

F11 77 s 1 MAR 774.*

3.

2-

'I.

NS

--5%- S. aS S s

+Soz . . .

' B C A B c a-A C A a C

4-

3.

2-

I.

TROUTJUN 77

*

4.

3.

2-

1.

ANCHOVY

JUN 77**

S~I

4-

3.

2-

1-

. SHRIMPMAR 77 JUN77

* 1 **

85'S aa~

S , I

0|-^

5-sa

MS _uS . . r a. r o .A 3 C A B C A 5 C A B C

[From CFS, Vol. VI 1, Figure 6.41

5-32

Tide - The effects attributed to tide level were extremely variable

(Table 5.3-1). On all of the intensive transect studies, tide level

was generally significant (0.05 or 0.01 level), but it was difficult

to discern a pattern associated with this significance. Higher densities

occurred during high to mean tide levels in March and April 1977 when

freshwater flow rates were large.. On the other hand, higher densities

occurred during low to mean tide levels in February 1977 and June 1977

when freshwater flow was relatively small. No readily apparent

explanation of these differences was discerned.

Interactions of depth with tide direction were also variable both

within and between species (Table 5.3-1). There was no significant

depth-by-tide direction in February 1977 for spot, croaker, and

flounder; but there was significant interaction in March 1977. However,

the pattern of difference was not the same for each species. Spot were

apparently moving slightly downstream during March 1977 because of the

extremely low salinities upstream. Surface densities were higher on

outgoing than on incoming tides (Figure 5.3--B). Since bottom densities

were about the same on in- and outgoing tides, the net result would be

a downstream shift in density. Croaker, apparently not so adversely

affected by the relatively low salinities, were still concentrating at'

the bottom, especially during outgoing tides (Figure 5.3-8). This would

enable them to hold their position and use the net upstream drift in the

lower layer of the estuary to move upstream. Flounders, a species with

an ability to lie directly on.the bottom, showed that on incoming tides

surface and bottom densities were higher than on outgoing tides (Figure

5.3-8). However, this was not the case in March 1977, when flounders

did not appear to be concentrating upstream (Figure 5.3-7). At that

time significant interaction of depth-by-tide direction occurred,

because bottom densities increased in incoming tides, but surface

densities did not.

Menhaden showed significant depth-by-tide interaction in February and

March 1977, primarily because surface densities were higher than bottom

densities on incoming tides; whereas the opposite was the case on

5-33

Figuzr 5.34. intensive river tide direction vs. depth inwactions. -

- * PECIABtUTYt I-INCOMING I10 S-SUKFACS* I.05OABISLITY) 0-CUOING tl-t ISOt1OM

NS - NOT SIGNIF KANT

4.

3-

2-

11-

SPOTFEB77

us

& - INI

MAR 77*

F13 77CROAKER

NS I MAR774.

3.

2-

1*

1%~

**

'-SI-'

I S

o-b . u . .

i 6 i 0 i 0

*

0

-d I

FEB 77FLOUNDER

MAR771S -

s as.-. SI

4-

3-

2-

I MENHADENFEB 77 MAR 77

'**

.

'a*s1---,s------ _A

I5

U .

II . I I - i 6 i O

2-

11-

TROUT

JUN77NS

3-

2-

1 -

I

ANCHOVY

JUN 77 4-NS

S 3-

2-

I-

SHRIMPMAR 77 JUN 77

NS NS

I---- - 4$ S

S .s

- - , 0O I 0

,S

.oZ .

i i o 1 . 0

[From CFS, Vol. VIl, Figure 6.51

5-34

outgoing tides (Figure 5.3-8). This suggests that menhaden, like the

more benthic-oriented species, moved toward the bottom on outgoing

tides. This would help to minimize their seaward movement during

outgoing tides.

5.3.2.2 Larval Retention Study (LMS)

Behavioral responses for three taxa (spot, croaker, flounder) are

summarized in Figure 5.3-9. The basis for this diagram is the ANOVA

summary in Table 5.3-2. Note that in this program collections were

also stratified by depth, photoperiod, and tide and that sampling

was conducted at two locations (Buoy 32 and 50) on three dates,

March 14 and April 5 and 11, 1978. A partial data set was reported for

April 5 (see CFS, Vol. X, p. 5).

Spot and flounders were most similar to one another in their response

to water-column variables and tended to congregate near the surface

at night (Figure 5.3-9), but they differed somewhat in their behavioral

response to light and tide. Flounders exhibited a greater tendency

to settle to the bottom on ebb tide and also during the day. This

response apparently enables flounders to penetrate fresh water effectively,

and provides a means of upstream migration by saltatory motion.

Croaker, on the other hand, tended to remain in the lower half of the

water column for a greater percentage of time, therefore accumulating

and remaining in deep water near the head of the estuary. This funda-

mental difference in croaker behavior results in a different life-

history strategy (habitat selection) compared to spot and flounders,

which tend to seek shallow waters.

5.3.2.3 Abundance and Seasonality

River - In describing spatial distributions in the river, the grouping

of stations or segmentation (Areas A, B, C, and D) described by Copeland

5-35

- t

fligure 6.3-. CoiiApjuil modl log a Iaaa folnii m"ch&d based on* tao1 1 lp od tand m im -e

SPOT- FLOUNDER

NIGHT

CROAKER

NIGHTDAY DAY

SURFACE0

0

a 0

-Og 00 *

BOTTOM *.: . **.

* 0 0..* 0 0

_

* *0-

. 0

* . 0 . -

** O..- :O* 6 .

* . 0- O- a 0

S *O*O *OR - 0 00 0go

* ..

O _t .

* 0 0

0

*0..a *

0 ,

* . 0

a

. .a 0

0* ... .

* * 0 -0

* . . 0.0 O

00000

L.

SURFACE

A and

I

BOTTOM

r NON-TIDAL FLOW(UPPER LAYER)

I .. .* . *.~. .'G1

DOWNSTREAM UPSTREAM NET NON-TIDAL FLOW DWNSTREAM UPSTREAM(LOWER 'LAYER)

A - TIDAL RESPONSE (MOVEMENT TOWARD BOTTOM ON EBB)

A! - TIDAL RESPONSE (MOVEMENT TOWARD SURFACE ON FLOOD)

B - PHOTOPERIOD RESPONSE (BOTTOM ORIENTATION DURING DAY)

B' - PIIOTOPERIOD RESPONSE (SURFACE ORIENTATION AT NIGHT)Ifwats CFS., VL X, Figure U|

Table 5.3.2. Analysis of variance summary for the larval retention program, Cape Fear Estuary 1978.

offfaOor li !O16-It bag Y kP 11 11 XPR It 'AR UIR 11 ORS

Spot

bLre ut= ,pp.

Spot

ParI lreht #pp.

PfiQUOnX=DbSpot0-cakarZua.LLhZkrsa pp.

Spot

PROTO1 D I JDIPMSpot

0hatma

ba /ra

* C-al

1 DS 1)3 1>S3 as . t3S

na as AS

IL ELI LiSa1 Iii EII LI -n a

VS 0D) IDOnn 0)> 3)0DD 1PO ID0

>C as AS>f . na F>D

DE1 F>& D>E

t(3)) 1)3(as) 1>3

as (an) AS

- (as) IL IS- (AM) I l Ias (as) As

(ns) I)DD- Cam) I3>D* (as) )D0

(as) n.m- (1)1) as

F)1 (D1) rDc

AKD

U

DK0V

nlIehthys "pp.

tastjicat 0

Chaccel 0o 1 D

T=h I ST1?ZKIdspotnlood

CroakerFloodEbb

!a~aU.~Zzz pp.Flood

)S IDS 15 Sas D3O S>1A A ItI Li A

Li LA a LAS

PS D3S P5IDS a: asLi L1I LiIES. LS Do

as Its as

aas as na

02 I.sf ala

ma na ma

(3S5) DS(ma) AS

- (LAS) Li L

(mS) bS- (a)S) as

S _ (no) Eri- (sas) nn

na (as) 3)>

is (as) aS

na (as) aIL

- oa31 an- Coal nai

- Ina] na- tL YJ1 LL z

as (as) as

fi Cos] I "

TIDE I DEmSpot

fast/Vest

CroakerEat/vc~st

ChDmll

rZ1lh1 thz. appM.Eatat st

0hacna1

Floodobb

Flood

Ebb

FloodEbbFloodEbb

rEoad£abbFlood

Cbb

Ic na as3S na DSLIB a 5tLI X Lft5 LAS LXI

VS ' na na83) 3>5 PS3I I h LI iI

us as esas1 as AS

as Ms na4EL LI 5 -

na an Na

- tn a I n- (al D)5

- teal LX I

- Ins] DS- Cnsl LAS

- e Ca] E lItn al us

InsCa) =A.ns Inal Na

AU [na1 P3na tnal ns

bs;ths; Surftce (SI , 'id-4.pth (K) 30ttoo ().cftatoyertods; Day (0). Nignt (N).dTide.; Flood (F). Ebb (E).

Stations; East (E), CharceL (C), 'dwst (I).

ns - No 1±n3ificartt difatreunc,

- NO analysia eCCnducted.

C I . Daytim da only.t - Ebb tlde data only.

,L ~nr o wat t rUlt.S 3re 1n be.low latter deslgnations.

3- 37

-

(From CFS, Vol X, Table 41

et al, (CFS, Vol. VII; see Study Program Map*) will be used. The

occurrence of spot larvae and postlarvae in the system began in

December 9nd generally continued until about the first of April

each year (Figure 5.3-10).**. When larvae first appeared, they were

distributed throughout the lower three sections of the estuary (i.e.,

up to and including Area C (see Study Program Map) within a two-week

period. Spot did not occur in Section D until several weeks later

during 1977 and 1978 of the study, but remained there for several

weeks after they had generally disappeared downstream. The erratic

occurrence of density upstream in the estuary was generally reflective

of perturbations in the Cape Fear River flow rate, with the larvae

being forced downstream as flow increased and salt content of the water

column decreased and being carried upstream as runoff decreased.

Croaker began to appear in the estuary during September and October

of each year, and were there until mid- to late April (Figure 5.3-11).

After their first occurrence, croaker larvae and postlarvae were

generally distributed upstream in the estuary over the two-week sampling

gap--even into Section D. Freshwater flow rate reduced salinities to

near zero and also influenced the distribution and density of croaker

larvae and postlarvae upstream in the estuary.

Larval flounders occurred in the Cape Fear estuary between December

and April of each year, with their distribution also extending well

upstream immediately upon their initial occurrence (Figure 5.3-12).

The increased freshwater flow also affected flounders, but primarily

in the surface layers in Sections C and D.

Menhaden larvae entered the estuary during February and were there until

early May of each year (Figure 5.3-13). Dispersion through the estuary

was almost immediate upon the initiation of recruitment. Menhaden

larvae and postlarvae remained upstream for a month or so after the

recruitment had ended.

*Area E is used to denote entrainment information.

**A key to identifying trip and station as used in many figures andtables presented in this section is included on pp. 5-144--5-146. Trips aregenerally sequential from September 1976 through August 1978, and stationsare grouped by Areas A, B, C, and D as shown in the Study Program Map wiihlowest numbers corresponding to Area A and highest numbers to Area D.

5-33

Figure 6.3-10. 24-hour meua density of spot larvae in the Cape Fear River.

SPECIES-SPOT

0 3 6 9 12 15 18 21 24 27 30 33 36 39 92 4S 48

RIVER TRIPOf Ns Do J F * M u A, Me J o J * A * S .0 aN . DU J . F aMoA AMe J o J s A

1977 1 1978

(From CFS, Vol. VII, Figure 7.21

5-39

Figre 5.3.11. 24hour mean density of croaker larvae in the Cap. Fea, River.

' SvECit-CcRO9KEAR

~1.-

RIVER TRIP0. N. D* J I F I M I A M M. J I J , A * S Om ND D J * f iM* A *MI J I J * A

1 1977 1 1978

( From CFS, Vol. VI 1, Figure 7.31

5 -O 0

Figrn 5.3-12. 24-hour mean density of flounder laroa in dw Cape Fear River.

SPECIES-FLOUNDERS

GROUP C

4.0

3.0

~2.0 -

'0' 1.0

GROUP S

4.0

3.0

2.0/

1.0 ,f t1 1 1 '1 .

.. z~csa~aGROUP A

4.0-

o 3 6 9 12. 1S 18 21 2S 27 30 33 36 39 42 $5 Be

RIVER TRIP

CeN. D J F s M .A MJ * J * A uS .0 ,N. D. J I F oM * A ,M J * J * A

1 1977 1 1978

[From CFS, Vol. VI , Figure 7.41

5-41

* -Flgure 5.3.13. 24hour mean density f menhaden larsve In the Cape Fear River.- SPECIESIMAOE?

1.

18 21 24 27 30RIVER TRI?

O. N Ds JF If . A I MI * I I A *IS IO IN * a2 1977 1

J I F sM . A cM * J I J I A1978

(From CFS, Vol. V11, Figure 7.51

5-42

Mullet entered the estuary in December of each year and remained through

Hay (Figure 5.3-14). The population density of mullet was low compared

to the other major species, and it was therefore difficult to assess the

impact of freshwater flow on their presence. The density of mullet

upstream to Section D was very small compared to their density downstream.

Shrimp postlarvae entered the estuary during late February and early

March of each year.. This first recruitment wave was primarily brown

shrimp (Figure 5.3-15). The density of shrimp postlarvae decreased

to almost zero in May of each year. A new wave of recruits, composed

primarily of white and pink shrimp, appeared during the summer. This

population was in the estuary through about early December of each

year. River larval samples indicated that brown shrimp postlarvae did

not penetrate upstream in any great numbers, but did concentrate in the

C area of the estuary and as juveniles were abundant in the upstream

shallows (see also Sections 5.3.2.4 and 5.3.2.5). Pink and white shrimp

penetrated to Area D.

Anchovies appeared in larval samples during late April, with their

distribution being widespread almost immediately (Figure 5.3-16).

High concentrations of anchovies were found in the estuary throughout

the summer, with the density decreasing through the fall to early

winter. A few postlarval anchovies overwintered in the estuary,

particularly in Sections C and D.

Other summer spawners, the seatrouts (Figure 5.3-17), first appeared

in the estuary during early May and were there through September. Their

distribution was similar throughout the different segments of the

estuary.

The seasonality of the major species considered in this study seemed to

be relatively repeatable, including the sampling throughout the 1974-1978

study period (Hodson, Schneider, and Copeland 1977). High freshwater

flow during the late winter and early spring in 1977 and 1978 forced all

of the larvae downstream from Section D during a time when salinities

were extremely low. A noteworthy observation was chat all of the ocean

5-43

;Frgue 5.314. 24hour mea density of mullet larma In the Cape Fear River.-,SPECIES.ULLETS

4.0-0 - SURFACI+ - SOTTOM-

GROUP a

3.0-

2.0-

1.0-

ffY-\ AA A 4 A0.0- . , ,

GROUP D4.0-

3D-

2

1b _1i.0. i-am

GROUP C

N-

4.0-4

12

0.

4D-

-L_. -

GROUP a

3.0-j

2.0-

1.0-

Ia_ _Mv'-rl n - -_.v

GROUP A

2.0-

1.0-

/-'� 'A0.ri.._ I' V . T' I* I I-) I * *< . -Y I 1 - * - ' I - I, . .7 I . . I . I -J I I |I-- * . -

0 3 6 9 12 15 18 21 24 27 30 ;3 36 39 42 '5 48RI'VER TRIP

o., N Do J .f. M * A. M * J * J I A . S .O. N *. J * .M .A .M. J . J. AI 1977 1 1978

(From CFS, Vol. VIl, Figure 7.61

- ,'

Figure .- 15. 24-ur mean density of shrimp larvae In the Cape Fear River.SPECIES-SiIAI

o - SURFACE GROUP .

4.0 + - SOTTOM

3.0-

2.0- A

1.0

0.0wGROUP D

4.0

3.0

2.0-

1.0

0.0 aseaa GROUP C

4.0'

3.0

2.0-

4.0

GROUP A

4.0-

3.0-

1.0' & eD.

0369 121 18d212273033363942 5 8

RI'IER TRIPO* N* D. J . F * Mt .A iA ,h J * J.m A * S * O* N* D. J * f~ MA aM' , J . J . A

I1977 11978

[From CFS, Vol. YlI, Figure 7.7|

5 -.45

Figure5.316I 24homm da of 'anc arvaeintheCape farRiver. . _

SPECIES-FNCROVIES

N

1.a

18 21 21 27 30RIVER TRIP

33 3r 39 $2 5 :a

Ov No I D J IF I M I Al Ai$ J It J I A 1 5S* Ot No* Dog J *IF 'MI*A *M t J * Jo* A1 1977 1 1978

tFrom CFS, Vol. V1I. Figure 7.81

5-46

17. 24-hour mean densihy of sea trout larvae In the Cape Fear River. -SPECIES-SEATROUTS

o 3 6 9 12 15 18 21 2+ 27 30 33 36 39 42 5 48RIVER TRIP

O Nt Ox i a F I M * A *M o Jo J a A * 5 * 0 No Di

I 1977 I

J * F sMs A *MaJ a J * A

1978

[From CFS, Vol. VII, Figure 7.9]

5-4 7

I

spawners (e<.g, croaker, spot, menhaden, flounder, shrimp, and mullet)

were dispersed several miles up the estuary immediately upon the initiation

of recruitment, at least within the time scale encompassed by our

sampling every two weeks. With the exception of the mullets, all of the

species that were recruited from ocean spawning areas achieved some

degree of concentration upstream above the Sunny Point constriction in

the estuary, obviously taking advantage of the two-layered bottom flow

upstream.

*

Marsh - Peak marsh abundance of larvae and postlarvae in 1977 and

1978 reflected abundance in the river and occurred mainly in the winter and

early spring, coincident with the presence of spot, menhaden, mullet,

and flounders (Figures 5.3-18 and 5.3-19). On an individual species

basis, peak abundance was almost always associated with the recruitment

of postlarvae or early juveniles into the area, and subsequent decreases

in numbers were due to mortality and/or emigration from the primary

nurseries. Few postlarval croakers were captured in marsh habitats

compared to the high concentrations of this species in the river main

stem (Figures 5.3-20 and 5.3-21, upper left). Spot postlarvae dominated

the catches in the CFE marshes with peak densities in March of 1977 and2 2

1978 of 3,099 and 2,713 individuals/400 m , respectively (Figures 5.3-20

and 5.3-21, upper left).

Striped mullet were also common in the Cape Fear (Figures 5.3-20 and

5.3-21, lower left) except during the cold period in early 1977, with

primary recruitment of early juveniles occurring in March and April of

1976-1978. White mullet, however, displayed a more distinct seasonal

presence in the Cape Fear marshes. Young mullet arrived in May (in

both 1977 and 1978) and emigrated nearly completely from the estuary

in late fall (1977).

Other winter-spawned species were also common in che CFE marshes.

Flounders of the genus Paralichthys were most abundant in March and

A4e disussion D- -' 9 -a incu: es larvae and jveni'es sio.zthev were studied in the same sampling program, and it is difficult toseparate them for discussion.

5-48

aFigure 5.3.18. Total number of Individuals captured In the Cape Fear Estuary marshes, 1977.

IC0

NCE8

0

a20z

co

z

. 104

,lo2

J F M A M J J A S 0 N D

IFrom CFS, VoL IX, Figure 81M O NTH

aNumber of organiama/400 =2; nine stations; all taxa are included5-4 9

aFigure 5.3.19. Total number of Individuals captured in the Cape Fear asuarY marshes, 1978.

lo6

S

E

8

-I

0

5

0U.c

w

z

I I I i I I I I I I103

S 0 N 0 J1977

F M A1 9 7 8

M J J A

Number ct crganliSms/'L3 m-; seventeen statjions; all :axa are inclzed.

(From CFS. Vol. " Y, Figure 91

THIS PAGE INTENTIONALLY LEFT BLANK

A_

IFigure 5.3.20. Seasonality curves of selected species in the Cape Fear Estuary marshes, 1977.

4of%'Iv

310

2I0

* SPOT

O CROAKER

* RED DRUM

i,NE00

q)

2

0

z

LL

w

C:

- ..12

01',8,A-d

A

-r I I V1 TA i I

.14l0

3

10

l I

ldJO

* STRIPED MULLET

o WHITE MULLET

IV

-I %

- I

I II I I

- I bI I

I %I

r%.. -%..4n- -, \e

* BROWN SHRIMP

O PINK SHRIMP

A WHITE SHRIMP

* BLUECRAB

-*0%I' f~*;X.

'-,\R

:. N:. %

A -

II Ii I!

J F M A M JI I I I I I I I I I I4 F M A M J J A S O N I J

AI I I I IA S 0 N 0

MONTH MONTH[From CFS, Vol. IX, Figure 121

Figure 5.321. Seasonality curves of selected species in the Cape Fear Estuair marhis, 1978.

NS00ITGo

C9

0. 0

.. 0

Iw

zwCD

w

104_,-._

* STRIPED MULLET

O WHITE MULLET

A

, I-I o

l0' \u II a I

\ I

rv , ,

,_ _ I T

S 0 N O J1977

F M A M J

1978MON TH

I I I I

J A S O N1977

lFrom CFS, Vol. IX, Figure 131

1978MONTH

April in 1977 and in February and March of 1978 when postlarvae first

entered the marshes (Figures-5.3-20 and 5.3-21, upper right). Poselarval

menhaden reached peak densities in April and May of.,both sampling

years, and juveniles were fairly abundant throughout the summer and

early fall months, then generally emigrated from the shallows in

October when temperature_ decreased markedly. However, in 1978 a

second large peak associated with the movement of larger menhaden

into the area (mostly Walden Creek) occurred in May and June. The

majority of these individuals were older fish of a different year class

(probably 1+). The pooled data for menhaden also did not indicate

the large monthly variation observed for catches of this species. In

a given creek, densities varied over more than an order of magnitude

between months, and peaks of abundance were not coincident among

marshes. The only consistent pattern exhibited by menhaden was their

greater association as postlarvae and early juveniles with intermediate

to lower salinity waters. Except for their brief stay in brackish

water marshes as juveniles, older menhaden did not seem to be present in

large numbers in the lower-salinity portions of the estuary, and particu-

larly not in the river main stem. Their mode of feeding may have

contributed to this phenomenon (June and Chamberlain 1959, Jefferies 1975,

Durbin and Durbin 1975).

All three species of commercial shrimps (Figures 5.3-20 and 5.3-21,

lower right) exhibited distinct seasonal presence: early juvenile

brown shrimp were present in the high marshes as early as Xay, and

white and pink shrimp were first captured in July (with the exception of

a few pink shrimp collected in June 1978). For all three species, peak

densities in 1977 were recorded during the month of first appearances,

and young adults emigrated from the shallow marshes during the fall,

especially after October. In 1978, however, this was only true for

white shrimp, both pink and brown shrimp having appeared at low

densities prior to having reached peak values. Blue crab (Callinectes

sapidus) (Figures 5.3-20 and 5.3-21, lower right) generally were abundant

in all months, with a peak of postlarval recruitment in November and

December (not obvious here, but see length-frequency data, CFS, Vol.

IX, Appendix Tables IV-39 and 40). Apparently the absence of early

5-53

juveniles in January and February 1977 catches reflected heavy mortality

or emigration attributable to the extreme cold in these-months (note

also the depression in February 1978 for the same reason).

In general, the same species captured as larvae and postlarvae in the

Cape Fear estuary (CFS, Vols. VII and VIII) were captured moving into

and out of the tidal creeks. Densities of each species taken during

periods of maximum abundance in all tidal creeks sampled were similar.

Ocean-spawned species such as spot, croaker, pinfish, menhaden, brown

shrimp, and flounder were relatively abundant as larvae and postlarvae

during March of 1977 and January (except brown shrimp) and March 1978

(CFS, Vol. VIII). Estuarine-spawned species such as anchovies, trout,

and gobies were abundant during June and July 1977 and May 1978. Pink

and white shrimp were abundant in May through October of 1977 (Figure

5.3-15; CFS, Vol. VIII, Figure 3.2) and June through the end of the

program in 1978 (Figure 5.3-21) (see also Section 5.3.2.5).

5.3.2.4 Spatial Distributions

River - In general, densities in the river were highest in the channel

area of each station grouping (Areas A through D, see Study Program Map)

when larvae were being first recruited into the estuary (Table 5.3-2a);

whereas once the larvae had established residency, a shift in centers of

abundance to the shallows took place. Moreover, some species moved to

shallow areas rather quickly, while others did not move out of deep

areas until near the end of their recruitment season. A notable

exception to this pattern was the distribution of croaker which seemed

to utilize the channel areas of the estuary much more extensively

than other species (Figure 5.3-22). Species typifying a life history

strategy which resulted in their rapid distribution to shallow areas

(including the marshes) were spot and penaeid shrimp. Following the

initiation of recruitment, spot rapidly moved into the shallow areas

of the estuary (in Sections A, B, and C) (Figure 5.3-23). By February

*.

S- llow s-athens are 11, 12, 13, 23, 26, 26, -, 22, 33.Deep stations are 14, 25, 27, 34, 35, vh, 37, 41, 42, 43, 44. Intakestations are 21 and 22.

5-54

Table 5.3-2a Duncan's multiple range comparisons of mean densities [1o9o0(density + 1)1 of larvae and postlarvea In different areas of the river(Channel, haillow and Qgean stations In areas A. ID, C. Q and ILnake Canal at Wiface and Rsftom) and In the BSEP dischargesluiceway (Entrainment). Any two means not underscored by the same line are significantly different. Significance is at the5% level.

I

Spot - Trips 7-9, 11-13, 31-36. 38 *nd 40.Silte lat-But Entr CSIh-Dot DCh-8ot aSh-Dot OCh-Dot ASh-Dot ASh-Sur Adh-Dot IX 1.917 1.892 1.865 1.860 1.831 1.782 1.778 1.580 1.553

ISh-Sur CSh-Sur lot-Sur ICh-Sur ACh-Sur Aec-lot C~h-Sur VCh-Sot AOc-Sur DCh-Sut1.379 1.310 1.288 1.261 1.097 1.041 1.031 0.738 0.722 Q.il5

Croakvr Tripe 7-9. 11-14. 28, 30. 32-36, 38, 40 and 41.Site Ceh-But CSh-Sot DCh-not Int-oot ltltr 8o1h-Dot DCh-Dot CSI-Sur AOc-Dot ACh-8otit 2.000 1.624 1.3113 1.271 1.231 1.114 t.O 53 0.970

Flosiasder - Tripe 1-9. 11. 12. 34-36 and 38.Slte CSh-Eot sls-flot CWh-oot ASIh-oot CSI-Sur DCh-Aot fSh-Dot Int-Dot Mt-Sur ASh-Sur

1.267 1.061 1.060 0.916 0.910 _ 0.910 0.872 0.863 0.669 0.634

He,,thdoss - Trips 11-14 and 38. 40 avid 41.Site DCh-Sur CSh-Sur CCh-Sur CSh-fut OCih-SBot CaW-Bt lot-Sut aSh-Sur ASh-Sur BCh-DotX 224 1 7SIL l.2-! 1.222 0.977 0.947 0.932 0.897 0.887 0.881

Orows Shrial. - Trips 11-14 a"sd 41.Sit. Entr ASb-8et Inct-B DSS-ot ASh%-Sur BM-Rot lost-Sur BSh-Sur :Sla-Dot Lt-SurX 1.626 14_I 1.015 oJ8_l2 .872 0.791 0.735 0.684 0.526 0.449

Whitl mid Plsk Snrlop - Trips 17-28 and 43.Site Esltr ASI-fot Int-8ut 85h-But C5h-Dot ASh-Sur Int-Sutr CSIs-Sur 8Sh-Sur *Ch-Dot

X Ijw44 .|240 .7 .2 1.080 0.970 0. 812 0.6 Q74 0,1

Aschauvy - Trips 14-24 avsi 43.Site ASh-Bot Elstr OLis-But AO:-Dtit oSb-Dot Ads-Dot CSh-Sur lnt-Sot CCh-Sur ASh-SurX 2.629 2.811 2.742 2.H13 2.575 2.552 2.469 2.439 2.423 2.394

ASh-Cot CMh-Sur PSS-Sur 8Q,-Sur ASh-Sur Int-Sur ACh-Sur DMC-Sur AOc-Sut0.945 0.878 0.854 0.854 As60N 0.595 0.566 0.403 0.:14Z

4Ct,-sur Riser aSh Suar Bch-Surn -17- A 416

4A0-Bot Int-Sur AOc-But ACh-Sur AOc-Str0.492 0.413 0.387 0.207 0ZQ ..a

Int-bot AOe-Sur Cntr ACh-Sur0 151 n It n a, I As zat

D53ms-Sot VCM-Sur ASh-Dut Adh-Bet ADc -DotS.. . JO u.U~ .. .. o U.J. S. Ass

_. - - .. - - -. 1. ... Io .. o1j ... A. .. I J. ...-

Ads-Dot CSh-Sur ACt-Sur Cdtl-Dot0.448 0.436 0.385 0.372

CCh-Sur hOc-Not AtC-Sur DCh-Eot liCit-Sur

0.271 0.248 0.234 _ 0.07 0.024

Ah-Sutr AOc-Aot DCh-Sor AOc-Sur DMh-Sot0.6411s O-. 0.331 0.292 0.245

BCh-Sur CCh-Dot0.653 0.631

AMh-Dot CCh-Sur0.572 Al (AR

CSh-8ot Aeh-Sur CMh-Dot lOt-Sur oSh-Sur ACh-Sor Vth-Str Ahc-Sur Ith-Rot2.353 2.346 .11f 712.117_ 2 1t2 '.048 8 1.?AL... 744 1. L..

Troist - Tripw 16-23 and 43.Site tlxts-Ds~t acls-Rot CSh1-But Ceti-Dut Mit~ot Invt5vit Ads-Sot Entri 1.321 W5J8 0..j1 .. 1,8..s2.1L] .f27 0,73

-

ASh-Dot aSh-hotA.fl2l 0.605

C~h-Sur ASh-Sur C~lt-Sur 8Dd-Sur0.564 fl.406 _ .. 7 a_1%R_

ls-Str RSh-Sur Age-Sur ACh-Sur Ant1-urIIA76 n 0Ln n sq it 0(3 2 0.5

F55*** Cy:;. V'ti . V II I * taIse I7. I1

I

FKus.5.-122 UnTAu* CO"AtR Posity ,(SUFA& -a * BOTTOM ---. I

I1s-n

I7

3I'

24

I ~--I '- cx-'' 'a --- " -5

Or , . _ ,

2 4

11�- - zsl-�I J / . -c -:

O& --I ',r14 13 ; 1I; ZS 27 2e 22 24 22 : 37 2. 2 32 :1 1_ 34 41 42 '-. "4

STAtION

[From CFS, Vol. VWI. Figurs 7.11]

5-56

FIGURE 5.22 (CONT.) UPSTREAM CROAKER OENSITY w W.S_

".-s

_;-''. , . . . . . . . . . . .

. , . v , , , . . S .

_1

9l-r --r, a'S -a, X ,~ "

31S.

WII I

,a- - _.-' k-a

a L A.

...... ....... , , , . - -d

3 _,K

1 .e< a , ' .14 'Z °~---4 ' a -3i

=2 %~

I .Ir ~ 'ia A.. -- **

o1

- C -

- I

36:1

Li

14

* ,0

0 a6-.-a--' -a--a-- .

~1- -~J. . a- --- a- A-*- *a4

- -

s =`5 .--.3, .

a 2 - 2 - 42 3L. la 13 Is is n7 2* ,, 24 ,, II ,t 24 1 :2 3. 34 .4 .,1

(FROM CFS, VOL VIl, FIGURE 7.111

5-57

Fiouts 5 UPSTnZAM SPOT oINSITT ISU3RFACI B AOTTOM -)

0 ,. ............

2

o .

1*.

Of.....- . .-- ...

AA

2.

+ a,~~~~- 'A- X,,,r,,,,,

I A -. X- . s i

0.2.

s

14 1S 12 II is 2,7 2`6 23 24 22i 21 37 34 2 31 3 3 1 42 ASTATION

(From CFS, VoL V1. .Figur, 7.101

;-;8

I

must 65.323 Icmtfd) UPSTREAM $PMT oRxswr (SUEACE4-4 SOTTOM -

2 I

3S

l -- a &ia4<

,. .. . -. .. .

4-. , a-"a

"' 11 a = 4

3. .

1 2

14 12 Ii 23 27 2i 23 J2 2 21 37 34 32 32 31 32 34 *1 42 43 4

STATION

(From CFS, Vol. Vil, Figure 7.101

5-59

and early March, densities in each of these three sections were generally

highest at one of the shallow stations. Only when low salinities or

low temperature caused a change in distribution did densities in the

channel stations tend to increase.

Postlarval penAeid shrimp (browns, pinks and whites) moved out of *the

channel and into the shallow areas of the estuary very rapidly, as

noted above (Figures 5.3-24 and 5.3-25). Rarely were the densities of

shrimp higher in the channel than in the shallows.

Other species, including flounder and menhaden, generally followed

this pattern, differing only in minor detail. Menhaden, however,

tended to be associated more with open waters at their later life

stages (postmetamorphosis), making only periodic forays into the

shallows. Like older menhaden, postlarval seatrout and anchovies were

quite variable with regard to their densities in the shallow and deep

stations; i.e., discernible trends were not apparent (CFS, Vol. VII).

Marsh - Comparisons between marsh densities of larvae and postlarvae

with that of the adjacent estuary and within the tributary creeks and

rivulets* indicate that a continuous increasing concentration gradient

occurs from the estuary mouth to the marsh headwaters (Figures 5.3-26a

to 5.3-26d). Despite differences in collection methodology, which may

account for some of the density differences, this concentration is

measured in orders of magnitude and serves to highlight the crucial role

of the marsh system as nursery habitats.

As a further example of this phenomenon of marsh concentration, data

were collected at several marsh rivulets during 1977 and 1978.

Although the results are based on a limited amount of data and field

observations, it appears that, even in these very small tributaries,

ocean-spawned species such as spot and mullet established substantial

populations. On numerous occasions during May and June of 1977 and

A rivulet is a small stream of water traversing a marsh and. iswholly contained within the marsh.

5-60

FIGURE 5.3.24 UPSTREAM BROWN SHRIMP DENSITY (SURFACE &--A BOTTOM

1977-78

41 -- -- --

1976-772

14 -- -- -,

13 I ' A I ,o : . H i - , _. _, ,~ , ,~ ,_,_OP-

0 '

22* 12

I1 S 2--^-- - --- -_

NO SURFACEA' SAMPLES

14 13 12 II 25 27 26 23 24 22 223 34 41 424,

STATION

IFrom.CFS, Vol. VII, Figure 7.141

03Ocn

Ul

I R.

123

-4

on

FIGURE 5.3-26a DENSITY OF SPOT

I ( Leiostomus xanthurus)DURING PEAK LARVAL RECRUITMENT

CAPEFEAR AR EA-W7?I00 pOO

Iopoo

E000

U,

0w

1000

100IL0

wco

z

10

FES APR MAY JUN JJL

1977

5-63

FIGtMEM13-26a(con'd) DENSITY OF SPOT(Leiostombs xanthurusi

DURING PEAK LARVAL RECRUITMENT

CAPE FEAR AREA-1978

100,000

NCSU. ANCSU BNCSU CCPL OCEAN At~LMS MARSH .

30,000 _

0

I N/-e

co/oU. IN I

o - .A * aN~

an A

LU '° S ,'! ' 'OCEA A,

WEXz

1978

FIGURE &326 DENSITY OF CROAKER

Micropoganias undulatus

DURING PEAK LARV4L RECRUITMENTCAPE FEAR AREA- 1976-77

100,000 C.PaL OCEAN

NCSU ANCSU B

_.------- NCSU C-.-. *.----LMS MARSH

10,000

e_E_00o 1,000_

0f

LU. 1000

eI

'\J

1976 1977

3-6 5

*of croaker upstream had considerably increased (Figure 5.3-28). Other

species followed this same trend. Spot, flounder, and menhaden also

concentrated in upstream areas, but not as rapidly, nor to quite the

same extent as croaker. Densities of these species were significantly

higher in Section C and/or Section D during most of the recruitment

period, especially late in the season (Tables 5.3-3, 5.3-4, 5.3-5,

5.3-6). Even though shrimp and anchovies were found in large numbers

in Areas C and D, concentrations in those sections did not dominate

(Tables 5.3-7 and 5.3-8).

Immediately after their recruitment to the estuary, brown shrimp post-

larvae move into estuary Areas A, B, and C (see Study Program Map) and into

tidal creeks and marsh rivulets (Figure 5.3-29). Although population3densities in the estuary were relatively high at this time (100/1000 m

densities of brown shrimp postlarvae in a Walden Creek marsh rivulet

were about 10 times higher (1000/1000 m3) than in the nearby river

Areas A, B, and C (Figure 5.3-15) or creek (Figure 5.3-29) almost

immediately after recruitment began. During this same time very few

postlarvae were found further upstream in the tidal creeks (including

upriver tidal creeks) because salinities in these areas were low.

Neither were they found in Dutchman Creek because salinities were too

high (CFS, Vol. VIII, Table 3.1; Vol. IX, Appendix III). Brown shrimp

postlarvae cannot tolerate low or high salinity when the temperature is

low (Copeland and Bechtel 1974). However, by May when temperatures in

the high marshes were above 200C, brown shrimp moved into these areas in

large numbers (CFS, Vol. IX, Appendix IV). An important point with

respect to the distribution of brown shrimp is that they are not

entrained or impinged at a size range of from 15 to 50 mm (Figure 5.3-29a).

This fact, coupled with the length-frequency data from the high marshes

and rivulets (CFS, Vols. VIII and IX, Figs. 12 and 13 and Appendix IV)

which clearly show that at this size range brown shrimp are residents

of tidal creeks and rivulets, indicates that once brown shrimp reach

their primary nursery areas they are not affected by BSEP operations.

It should also be pointed out here, based on the low numbers impinged

during late spring and sumer, that other species such as spot and

flounder are not affected by plant operations for a period of 2-3 months

1t0

S -'. -.

.1

- - He lo

FIGRGE 5.329 24-HOUR MEAN DENSITY OF CROAKER BY STATION PM DEPTHMARCH 1977 VS MARCH 1978

", iI

'_. 4

STATION

[From CFS, Vol. Vil, Figure 7.301

I . il -. ;

I

Table 6.3-3 River density gpoup CoMnpafrSon Loglo (Density + 1). Spot

1977 T I I P S 1978

7 8 9 104 11+ 12 13 33 34 35 36 37+ 38 40Cro.op mA *a &* mia *am ma am *a A" ** ma am m

Oulcall'a HR A B C D B C A D C B D A A N D C C H A D C BIA D S D A A 5 C Q A B C D A C A D A C * D C 8 A D C B A DD _ ADeptis ma am -m m- ma fma &A ha It Am

buncasi a Rtlt 8s S B>S Dis B3S laS A a A 5,5 B>S B3S 8>s BAS a S

Crp&Dep *A Hs a A *a am *m Am & as am aStation A a* m* &a mm am *m mm hmt *a ma am

utep*Sta NS a *a a NS a *a ma am mA

D)unrns'e tlR N>UD l4.U 214) 14) U>D N1ID 11)D NM M) NI)D 111- 1)b 11))1D 14C411K10-M uS NS a ah mm mA Am uS Ns am *m m am NsLjtpAD-N NS *4k he *A * 44 4* * a* *6 uS *A

Tide-Dir HS NS S NS NS A uS * a NS NS am NsDittcan's MRN In'out outle out,-In Sn&out outAtn In-out

t: phT-U1 NkA S NS *& NS NS & &* uS uS NS NSavpat-U Af HS NNSma al NS NS a t NS NS

I U-M*^TU NS NS NS Ok NS a* NS us NS s NS m S

X 0.997 1.348 1.585 1.628 1.818 1.391 1.244 1.449 1.135 1.546 1.760 1.154 1.449 0.997S .525 .491 .597 .579 .531 .540 .513 .476 .463 .454 .354 .622 .563 .513

4 mesbutassclaI tualg 8at-mm 0.01 probablllty

A 0.05 probability

tro.. EEs. V's I. Vt I, Tab I e I. I

Table 53-4 Rlvevo density Or-sp Compauions Log1 (Desity 1). Flounder

1977 T a I t 5 1970

Source 7 8 9 10+ 11 12 34 35 36 37+ 38

t roup AC AC A * i tC ** A& &A As *C CA

Duncan's tR C t A D D C 8 A D C A S D 8 A C C D t A D C A 8 CA D C A C A D C 8 A C D a A

Deptl VA CC *C ** C* W* CC C* -A

Duncan's MR 5b'S R15 IB'S a's s2s I'S I'S O>S PS 11>5 D>S

CrpaDep HS Hs NS I RS hs a* *6 fp As

Station *C aC C CC C C As As as CC

Dep*StA HS *W C NS j M NC. N5 as e5Day-Mite as S. CC a* *C C* *A as

Duncen'o HR N>'D N>D N'D N>D N>D MID N'D N>'D WID iD N'DCrp*D-N O Ca CC A, 1NDepCZ-N As *C as "S CC CC CC CC CA CC CC

Tide-DBr "S AA CC * CC CA *e CC CC CC CC

Duncan's MR Inout jn2out i)ut Jnlout In"out in3out Inotut In3Out InwoutCrp'tT-D as NS "S a "S "S as " NS as "S

Dep*T-D "S NS "S Ns Ms "NS *O "SD-NAT-D *C a ifS "S uA NS CC NS "S *

i 0.561 0.912 0.729 0.512 0.679 0.460 0.886 1.329 0.987 0.923 0.845S .554 .468 .519 .433 .512 .477 .532 .539 .460 .454 .487

u aubstantlal missing dataCC 0.01 probability

A 0.05 probability

From CFS, Vol. Vll. Table 7.3

Table 5.3-5 River density Woup comparisons Loglo (Densty + 1). Monhaden

1977 T R I P S 1978

Source 1II l+ 12 13 14 37+ 38 40 41Group sh ** * &A I ha ** A

De caN KR DA A C C AD C DA D C A D C & A C 11 AC D * D C b A D CA

Duncan'e Hit 53 Sb S>38 S3 S.2l S'S 5" SBNCrpaDep NS hi a * *fa ef *&Station *h *a aiDep*St h* M NS & NS *a so uSDay-"Ite h* kw * a* NS a* *. .

Duncansu MR N>D W'D NMD N0D N2D NWD NMD M0D N).0Crp*D.- LA hi NS NS *A NS *h uS asDepiD-N Ah NS a HS hA* Ns MTide-Dir a NS NS NS & *hi kk *h a

DuMncan's R Ifnout in'Out lnWout lnDout 1nsout ln'outCrp*T-D NS NS h u NS a hh h h hhDepAT-D *i *a hi h* oh h ha NS O*D-NAT-D NS KS a NS Nh NS ai sa

X 0.822 0.894 1.376 1.465 0.402 0.566 1.294 1.081 1.074S .548 .518 .644 .615 .432 .437 .510 .552 .554

+ *ubutantial asIing dateh* 0.01 probability

a O0.0 probability

N

U1-I

0',

Frum CF'S. Vol. VII. Table 7.4

( (j-) ikD-1. .

Table 6.3-6 River density group comparhsons Loglo (Density+ 1). Sea Trout

1977 T R I P S 1978

Sourrce 16 17 1B 19 20 21 22 23 41 43Croup

Duncuan' s MRDepthI

D)uaicall ' s MR(;rp1*)epStat JfonDePAkSLal)ay-N i te

%'i Dusicimi s MR

_J l;rp*D-NDep^U-NTide-Dir

I)taoicn' s MR(Grp*T-DDelj*'r-D)U-NA'I'-D

S

**

D A C U**

a>s**

NS

NS**

N>D

NSNS

I11;,out*

NSNS

0.464.51(

**

H C A D**

B>S**

**

*A.

N>D**

NS

NS

NSNS

1.008.613

**

H>S

**

**

**

N>D*A

NS

NS

NSNS

1.124.572

I*

D C B A

B>S**

**

A*

N>D**

NS

NS*

NS

0.872.564

D* **

A B C D C A B** **

B>S B>S** MS

NS NSNS **

N>D* NS

MS **

DAC

B>S**

**

NS**

N>DNS**

AC

in>outNS

NS

0.697.544

A*

D B C A

B>S

HA

N>DNS

lio>outNSMSNS

0.444.467

AC

NS

NS

ACNS**

N>D)**

NSNS

NSNSNS

0.298.397

**

C D B ACA

B>S**

A*

A

**

N>D

**t

NS

NSNS

0.780.523

NSNS

A

0.287.446

ln>outNSNSNS

0.620.586

*^ 0.01 1)rUbabilILy

A 0.05 priobability

Frumt CFS, Vul. VI], Table 7.7

Table 5.3-7 River density group compaisons LogIO (Densty + 1). Slimp u

C

-1917 t kl 1 918Araw" Shrlop

Source 114 12 13 14 4Croup 44 44 *R 44 *

Duncan's MR A D C A A CA§ L SLA P A aDeptis a A4 * *4 uS

Vuacan's HR PS Sa's m4sCrp6Derp H9 ** i* 4 usStation Am *4

Dep'ata HS *e uS uS NSDay-Nte ** ** A* **Duncan's MR N>"D N'0 N)D NOPD ND

Crp*D- m * eme a **Dep*D-N am *a am me m*Tide-Dir as 4* a us *0

Duncen'u HER Iniut Imiotat IV ont in)@.t Inieut

CrpAT-D NS 4* uS 1*Dep&t-D NsS NS NJ NSD-N,4T-D am u4 N5 4* NS

1 0.422 0.6Bd 0.614 0.454 0.503S .462 .461 .534 .536 .442

3

.- I

C))

1LL

SourceGroup

Duncan'e HIDeptif

Duncan's tUCr pDepStationDep

4Sts

Day-NiteDunean'e HR

Crp*0-NDep*D-NTide-Dir

Dutcane' HRuirp&T-V

DepAT-DD-NAT-S

S

_

1 1

ACOA 11 C D

"S4*

*u.4*

4*

NSIWIout

NSNSNS

ii

as,A C S D

&A

4*S

I'l

a.04*

NsD

NSHS

19*A

S A C Q

* .*6

Hs

N-D

*4"S

NS

Oka

NS

NS

20

8 A § DNS

N5

*i

a.

usIn"eut

MSNS

-21__

C A B D

*>SNSus5,5

NS

MCD*4

4*.

4*

iniout

NSM8

22

S A C D*4

u'sme

N8

.4*

.*

MS

Ms3,

23

P A C Vi*S

4*"IsD4*

*4

N).Vus*4us

Aa

*4

24

A C *1 D

44NS4*

*4

'ID4*

4.IM*

1nieut

MSNS

-

26tme

AC S DNS

*4

Wu'S

us

AsHSus

I 11 I t a 1978

44 44R &*__

A 81 _ D a C A D>SC~a's

Ns US4* *4

N>D N.D4.1 11450

MsusN: N

NS us

0.663 0.909 0.555 0.648 1.2291 0.652 1-330 0. 66 0.713 0.473.560 .678 .658 .594 .663 .700 .1S 0.603 .59S 0.43 0.378

488

* subutantlal *siming date

'* 0.01 probsbllity

* 0.05 probability

IF.. (:s vl Vll, Table 7.5

Table 5.3-8 River density group comparisons Logjo (Density + 1). Anchovy

V

1977 - R I P s 1978

Source 14 1S 16 17 18 19 20 21 22 23 24 43Group

Umncfl a MHRDepth

t(rp*DepStat Itn"

U1 DepAStaI Day-mite

. f Duncan's MR'0;r1 lA-H

DepAD-NTIde-Dir

DuVIChS16 HRCrphT-JIDepAT-bD-NAT-D

xS

A S C D

5)8

Sa

ha*A

HSNshaA

o01t . In

NS

1. 164

.624

aa haACA A&C

A C S D A 5 C D

h~,a ha I

* aa

NS *NNs D

^*d *4

*k NSha us

A R C D)_ _ _a

ha

NS

a.

In"outNA

MS

A C 1D

*h

"S

N>D

N5NS

1m,'out.

NS

C ;"A D

*a

"S

NS

N4SNS

N5Insout

H5

N5

11 C DAEC

B>SaNS

h"a

*aha

A CR11 QhA

I's

*a

ha

I.:.ha

ha

NSNS

a*

It:5 C 11D

MSha

MS

out 'S.,

ha

"SS

NS

haD

. *

NS

as.

a AC 0

ha

haD

fta

A C*11 D

::eX

N>Q

NS*a

NS0

*S

2.493.499

ha

NSha

2.094 2.451 2.654 2.959 2.692 2.582 2.238 1.956 1.883 1.305.51 .468 .511 .481 .562 .464 .498 .592 .492 .496

hh 0.01 prubhllILtyA 11.05 probabIllty

rV.,o CFS. Vol. Vll, Tnble 7.6

-

24 HOUR MEAN LOG 10(DENSITY+l) OF SHRIMP AND SPOT IN WALDEN CREEKFIGURE 5.3-29 AS NSE

MARSH AND AREA R.C.F.R. (COPELAND. HODSON AND MONROE 1979)

- RIVER STAlION 24 DOTTOA -- MARSH STATION 61 RIEGULARIVER STATION24 SURFACE 0 AARSH STATION 6IROI0NO=1

. ~SHRIMP

1/ A/

2-

U'I. _

oI C pm

: \o '|0 SPOT 1N I

.,A,,-,

/ -

, . .. 1. . .. ..F I A I

I *. . .

A Av I.

AA .1

C) J P M A j4 ; i A A 0 N 0 i ; A i I J

Figure 5.3-29a Theoretical entrainment-impingment transition for brown shrimp (Penaeus aztecus) based on

22 the relationship of body size to traveling screen mesh dimensions.PENAEUS AZTECUS

20

18 Mesh size of *traveling screen (mm)

16S - 953 a '* 40 0

* 0 014- %

Ef maxx. entroinable size

I12- C

aas fn

010 ,- - - - - -- - -o0

min. impingeable size O o

m 8- ESa a3U er

6 -A BSEP entrainment 6-1-77

4- D 0.10SL1 + 0.0305 L/100 U Trawl. Dutchman Creek 5-19-77

NR2 1.998 0 BSEP impingement 6-1-77

2 - SD =0.728mm 0 6-21-77A A4 A

0- I a a 1 -- i

0 20 40 60 80 100 120 140

TOTAL BODY LENGTH (mm)

while they are residents of high marsh and upstream nursery areas (CFS,

Va-; XVII, Figures 24a and 12a).

White and pink shrimp exhibited similar patterns of rapid distribution

throughout the estuary immediately on recruitment to the estuary

(Table 5.3-7) and soon moved into the marsh nursery (CFS, Vol. IX,

Appendix IV-38). It is suspected that most of the suimer concen-

trations in the lower estuary were pink shrimp, which prefer higher

salinities (CFS, Vol. IX, Appendix VI, Fig. 7). This explains the

lack of concentration in Area D, as shown in Table 5.3-7. Few white

shrimp were taken in the CFS Studies (CFS, Vol. IX, Appendix IV) in

either 1977 or 1978.

The concentration of organisms upstream was drastically influenced by

changes in salinity (i.e., river flow) and temperature# To test the

impact of those influences, a quadratic model with two variables

(i.e., temperature and river flow) and their interaction was utilized

to test the validity of the relationship (Neter and Wasserman 1974).2As shown in Tables 5.3-9 and 5.3-10, the high r values indicate that

the quadratic model used was predicting effects very well for spot and

croaker.

That density of spot in the estuary is related to hydrographic conditions

in the estuary is shown by predictions of the quadratic model in

Figure 5.3-30.

Low temperature generally decreased the ability of spot to withstand Low

salinity. Therefore, under these conditions, the density of spot in the

downstream areas increased with river flow, whereas density in the

upstream areas decreased (Figure 5.3-30). As temperature increased, so

did the ability of spot to concentrate in the upstream areas under

conditions of high river flow. Thus, when the temperatures approached

200C, spot were most abundant in either Area C or D. In other words,

spot tended to concentrate in the more downstream areas (Areas B and C)

of the estuary during periods of low temperature, only venturing into

the ups:ream _._ (.x-v D) -.. an sal .-:-; was relaciively high. AC .id-

range temperatures spot were generally equal in abundance in Sections A,

B, and C, regardless of the river flyc conditions; but they did Ed: mv'

5-81

Table 5,3-9. Results of quadratic model analysis on spot logi,) (density + 1)

ParameterIntercept A

BCD

Estimate0.5360.9871.7191.670

StudentsT For Ho:

Parameter - 00.601.111.941.88

Std. ErrorEstimate

0.8870.8870.8870.887

Of

Temp ABCD

Temp2

Flow

Flow2

ABCD

ABCD

ABCD

0.2340.1640.131-

-0.063

-1.205-0.953-0.8780.229

0.5150.170

-0.695-0.880

-0.042-0.0140.0430.086

2.131.501.19

-0.58

0.1100. 1100.1100.110

-3.09-2.44-2.250.59

0.3900.3900.3900.390

1.530.50

-2.06-2.61

0.3370.3370.3370.337I

A.

-1.09-0.381.142.25

0.0380.0380.0380.038

Temp*Flow ABCD

-0.0230.0010.0450.028

-1.050.032.031.25

0.0220.0220.0220.022

_ E - .087R - .895

ITable 5.3-10.Results of quadratic model analysis on croaker 16g 1 (density + 1).

_ .

StudentsT For Ho:

Parameter - 05.20

ParameterYear-1977 vs. 1978

Estimate0.370

Std. Error OfEstimate

0.071

Intercept

Temp

Temp2

Flow

Flow2

Temp*Flow

ABCD

1.1861.6330.9451.569

ABCD

ABCD

-0.049-0.0340.1210.078

0.003-0.145-0.547-0.362

0.2810.1510.360

-0.787

1.662.291.322.20

-0.69-0.471.681.09

0.01-0.57-2.13-1.41

1.000.54,.1.29-2.81

-0.59-0.70-2.172.26

-1.21-0.08-0.67-0.29

0. 7130.7130.7130.713

0.0720.0720.0720.072

0.2560.2560.2560.256

0.2800.2800.2800.280

0.0340.0340.0340.034

0.0130.0130.0130.013

.ABCD

I

ABCD

ABCD

-0.020-0.024-0.0740.077

-0.016-0.001-0.009-0.004

MSE - .097R2 - .823

Il

FIGURE 53.30 PREDICTED 24-HOUR MEAN DENSITY OF SPOT AS A FUNCTION OF RIVERFLOW AND TEMPERATURE.

I

ORCUP A GROUP a

2

I-

z

a0

la.0O ,

Oaoup C CRouP D

"I

U

z

2

(From CFS, VoL V11, Figure 7.351

5-84

into the D area, except under conditions of lower river flow. As the

temperature approached 20 C, spot tended to remain in the C and D area,

regardless of salinity. When river flow was extremely low, the density

was highest in D, whereas when river flow was high, density was highest

in C (i.e., there were fluctuating nursery zones).

With some exceptions, virtually the same pattern was observed for the

distribution of croaker in this quadratic model (Figure 5.3-31).

Unlike spot, croaker seldom have their highest density in the downstream

areas, regardless of temperature and river flow conditions. At

conditions of low temperatures (5 C), croaker did move downstream some,

having similar predicted densities in the B and C sections and also

relatively high densities in the A section. Even at such low tempera-

tures, river flow did not appear to influence the distribution of

croaker, except in the uppermost regions of the estuary (i.e., Section D).

At mid-range temperatures (12oC), croaker showed a marked tendency

to move upstream. Here again, river flow exhibited relatively little

influence on distribution of croaker, except during periods of low flow

when they moved into the D area. Virtually the same pattern was

predicted at high temperatures (200C), except that densities in all

areas were low, probably because conditions of relatively high

temperatures for croaker occurred primarily at the beginning and the

end of their recruitment period when densities were low. In summer,

Section C of the estuary appeared to be the preferred area for juvenile

croaker (CFS, Vols. IX, XV). Salinity seemed to dictate their movements

upstream to the D area. They reached their maximum density there during

periods of low river flow. On the other hand, their movements downstream

tended to be dictated by temperature (Figure 5.3-31).

Marsh - Shallow tidal creeks, rivulets, and marsh shoals of the Cape

Fear River harbor dense resident populations of postlarvae of several

marine-spawned species. Field observations suggest that young fishes

and shellfish are actively seeking the creek headwaters; in effect,

the marshes first fill up with postlarvae at their headwaters. Post-

larval s-ot, mulles, frounder, red drum, and other species were :ser-5d

co reside in great numbers in the upper reaches of the creeks and

gradually decrease in densities downszream. Ichthyoplankton to-ws in

sI'I

I

I

FIGURE 5.3.31 PREDICTED 24-HOUlt MEAN DENSITY OF CROAKER AS A FUNCTION OF

RIVER FLOW AND TEMPERATURE.

OROUP A

-

b.

U8.

a6'

azUi

S1

+

U1

is22I

I

otouP c

(From CFS, Vol. ViI, Figure 7.361

creek mouths and a short distance upstream in these same creeks

yielded much lower concentrations than collections closer to the

headwaters. Furthermore, as individuals grew, they gradually

emigrated downstream, with older fish moving freely throughout the

marshes, as indicated by the increased patchiness of individual

species in monthly collections later in the growing season (CFS,

Vols. VIII and IX).

The foregoing relationship does not, however, hold for all postlarvae

that.use the Cape Fear estuary, Croaker, for example, seem to prefer

the deeper water of the river from the-vicinity of the salt boundary

through the mesohaline zone as postlarvae. This species was noticeably

absent in the downriver marshes, and densities were generally low at

upstream marsh stations, although there is ample opportunity to utilize

extensive marshes. Only one specimen of the 1976-77 year-class was

collected in these stations before May when juveniles appeared at low

salinity stations. In the early stages of recruitment for the 1977-78

year class, however, low densities of postlarval croaker were

collected, principally at Hechtic and Barnards Creek (Figure 5.3-26b).

Compared to the use of marshes by spot, therefore, croaker

prefer the deep-water, upriver nursery zones, as Haven (1957) and

Wallace (1940) observed for the Chesapeake Bay. For most Atlantic

Coast estuaries containing deeper channels, this relationship seems to

hold (Welsh and Breder 1923). In the Gulf of Mexico, Nelson (1969)

reported a similar occurrence of young croaker in the Mobile Bay ship

channel, as did Suttkas (1955) for the deeper waters of Lake Ponchartrain;

however, croaker also use the marsh shallows extensively in other Gulf

states, including Louisiana, Texas, and Mississippi (Herke 1971, Parker

1971, Arnoldi et al. 1974, Yakupzack and Herke 1977). Perhaps minimum

temperatures during winter recruitment in the Cape Fear and other middle

Atlantic Coast estuary marshes are limiting for this species (Joseph 1972).

Marshall (1976) has stated that standing crops of nekton in shallow

North Carolina marsh habitats rank among the highest values reported for

estuarine zones. Employing similar sampling techniques to those used

in cL-e CFE studies, including the use of l-mm mesh seines, he reported

5-87

densities of spot, mullet, menhaden, and brown shrimp to exceed 0.1/m2

in two marsh areas altered by ditch construction for mosquito control.

Marshall's survey of the literature (1976) paralleled his observations,

and even higher densities for total nekton were noted in the studies of

Turner and Johnson (1974) in South Carolina tidal marshes. However,

Marshall cautioned that the efficiency and selectivity of gear used to

study various estuarine areas may, in part, be responsible for some of

the differences seen among areas. Average densities in the CFS studies2

for the same species listed by Marshall all exceeded 0.1/m except for

brown shrimp. When seine data alone were considered for brown shrimp,2

however, densities of 0.1/m were recorded (CFS, Vol..TX, p. VI-3). Thus,

standing crop values for nekton in marshes of the CFE equal or exceed those

reported for other estuaries in the vicinity of the Cape Fear (Marshall

1976).

As reported in previous studies, temporal succession is also observed to

take place in the marshes, with many species residing in the upper reaches

of tidal creeks and rivulets during their earliest period in the estuary

shallows. As they grow, they gradually m-ve downstream (Herke 1971, Dunham

1972, Purvis 1976). A similar successional pattern has been reported for

the upper reaches of the Chesapeake Bay (Haven 1957, McHugh 1967, Chao and

Musick 1977) and in open bay waters near the head of the estuary in South

Carolina (Bearden 1969), Louisiana (Thomas and Loesch 1970), and Florida

(Hansen 1970).

5.3.2.6 Growth

For all the species analyzed, larvae and postlarvae upstream and in the

marshes were significantly larger than those in the lower reach of the

CFE. Using spot collected in the river as a typical example (Fig. 5.3-32),

the mean size of larvae was about the same throughout all sections of

the river during the first part of recruitment, and the distribution

of sizes was relatively narrow (i.e., 13-18 mm). There was an increase

in the mean size of organisms throughout the system during the mid-

recruitment period with the mean size for spot, for example, up around

20 mm during 1977 and around 15-17 mm in 1978. During the latter part of

the recruitment period, the picture became more complicated as new waves of

i 4q

FIGURE 53.32 PIRCINT LENGTH FREQUINCY Of SPOT BY GROUP (A-g1.

K I-D

-C

-B

-A

-I

-D

-C

-B1

-A

1977

APR 13

362

481

t711

1104 : ..*----

SS 8 /\%9

1978

-D

_c

-B

-A

zU0U

U9A.

MAR 1

Itof

49@

1X48

3S'

2954

2267

† ..: A :%.

- a

- D

-C

- a

-A

JAN 11 JAN 17

I

-D

C

as

A

SCALE

I :lo

on168

I 1

is4

-E

- D

A25

LENGTH, mm

AI

7'

1217

2175

2173

5 10 I 5 20 5 10 15 20 25

(From CFS. V-.1 VII, Figure 7.201

. D9

recruits entered the estuary. The mean size in Section D, far upstream,

had increased to about 23 mm in 1977 and about 18-19 mm in 1978, whereas

the downstream sections during that late recruitment period had decreased

in mean size to around 12-15 mm (Figure 5.3-32).

Larval spot and croaker in the downstream sections (i.e., Areas A and B)

increased in mean length during the early phases of recruitment, leveled

out over a major period of that recruitment season, and then decreased

as the new wave of recruits entered at the end of the recruitment period

(Figures 5.3-33 and 5.3-34). However, in the upstream section (i.e.,

Areas C and D) there was no leveling out of mean length, and the normal

growth pattern seemed to carry throughout the recruitment season with

the largest larvae occurring at the very end of the recruitment period.

It is important to note that the decrease in mean length that occurred

in Areas A and B during the recruitment period could only manifest

itself if the resident larvae were moving out of those sections during

their growth phase into the tidal creeks and upstream areas.

Figure 5.3-35 attempts to summarize many of the perceptions discussed

above as they pertain to larval distribution. The position of each

species roughly corresponds to its center of abundance within the

estuary. It must be emphasized that these are statistical distributions,

that is, many of these species are likely to be found anywhere within

the estuary; however, the great preponderance of them are found within a

particular range of salinities, depths, or tides. Figures 5.3-36 through

5.3-49 also summarize larval distribution over time and distance upstream

for spot, croaker, menhaden, flounders, shrimps, anchovy, and trout.

5.3.2.7 Trends in Larval Abundance in the Cape Fear Estuary

The larval abundance in the Cape Fear estuary was subjected to a trend

analysis (Table 5.3-11). Larval densities in the river showed an upward

trend during the years 1974-1978 for all major species except brown

shrimp. However, because of identification difficulties, pink and

white shrimp were combined and the trend in abundance for these two

groups together do not necessarily reflect the trend for each species

5-90

-- . - _ . ... _'. _ a..wl rr.nn 1%jLvtj.

SPECIES-SPOT

GROUP C

GROUP AU,,In

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 4ERIVER TRIP

0 * Ji I J eF .M a A, M J . J a A . S * 0 * N D .J .F eM . A M .I, J .A19an 1 973

[Fromn CFS, Vs '. V!! Figu"re 7.211

5-91

3MM . %, qM111E

C.f,. FIGURE 5.3-34 2-HOUR t1E£N LENGTH OF LARVAE IN THE CRPE

SPFCTFRrCA FRK

FEAR RIVER.

4

i�

t1114

t

N0 - SURFACE GROUP I

O + . OTTOM

sD; GROUPC a

Ncm

_ . GROUP A

CY

0_ ,

-4

0-

C2

C3-14

LO

GROUP A

0lWV

P

0 36 9 12 15 18 21 24 27 30 33 36 39 '2 45 48RIVER TRIP. A . 5 . o.. NO- .J f* M *A-M*J . J . A

I 197S0- N. O. J *. M .A.* M *M J .J

I 1977

IFrom CFS. Vol. VIl. Figure 7.22]

5-92

Figure 5.3-35 General residence distribution of Cape Fear postlarvae.

Depth Distribution

Shallow Ubiquitous Deep

White mulletPink shrimpSouthern flounderBrown shrimp

Blue crabMenhaden

WeakfishAnchoviesStarhead drumCroaker

Salinity

ki,

ITI

Months

J

F'

Higlh Middle Low

flounders-

M

spot

stripedmullet

A_

M

croaker

brown shrimp

white. mullet __

J

J

___ pik shrimp white shrimp

A anchovies(two species)

S

0

N

1)

red drum

CAPE FEAR ESIUARVFIGURE 5.3-36 PLOT OF LARVAL DEN4SITIES OVER TIME AND DISTANCE UPSTREAM

SPECIES-SOT DEPMhBOTTOM

CcKTouR PLOT CF STATSTRIP

44 4. * * * . . . K * * K . . . . . . * 0

43 + . . 0 * ** * . . * . ..

Al **1 0 K x C .. 0 ..... ** * *

99 4

33 * a * . 0 U K . . .

32 + . . 0OXX UK .. . . o . * * a o o xM:31 + . . 0o * K KU K

35 + * . . x xx o * * . a . a 0K K0

36 + . S K 0 0 0 * 0 JO3? 4. . 0

un99 *Z ? f . K X .* ~ * * * X xK~

0- 24 I e o XX K . * 0 00 0 0 KKKKKx+-21 4 *. . O K XX O . .. .. . . K KK 0 0

2 2 + * . 3 K U26O*. . KO K 0 K S K

23 + . .0 XXX x . . . .. . * K K X 0099 4

99 + K K o * * * * * KU Ku 00

1 2 * * 0 X X xOK O . . . . * 0 K K .033 4 * * 0 K K . *** 0 0 *a x K 0 0

1 4 * .

I? x 0 K * *** 0a (

£ 6 * ( 0 K0

I .0 0 0 0 0 0 0 0 0 000 0 0 0 0 0 * *f O

1 3 5 7 9 11 13 35 17 19 21 23 25 27 29 31 33 35 37 39f 41'- ---3 -

TRIP

SYMHOL SPY SYMBOLSP

000000 0.0000000 - 0 5CO5702 KxKXX 1597xx- 2538CUUr O.5C65?02 - 1'.5397105 Eafteat 1-519n105 2 .5328508q c

-- ---- - � 0 W.J�%.awv

I

FICURE 5.3-37CAPE FEAR ESTUARY

PLOT UF LARVAL DENSITIES OVER TIME AND DISTANCE UPSTREA4MSPECIES-SPOT DEPTH-SURFACE

CONTOUR PLOT OF STAT*TRIP

U'

'.) 0

I-

STAT

43 442 *41 299 434 f33 432 431 a35 436 437 6.99 +2 7 +24 +21 022 4

. . . . .00 . . . o .o O* . . . . . 00 * 0 * * * * * * * . .

* . . . . . 00 * 0 0 . . . . . o o . * o* ... . . . 00 0 00 o o o .

, . . 00 0 o 0 . . . . * . .. .0 0 0 0 0 X x

* 0 0 D x 0 00 0 0 0 0 0

.0 o . 0X o x x * * * * * - - 0 -. . .O O O x O

. * K x Ox oxa * * * * 0 * * * . *

. o 0 0x o c o 0 0

. . 00 o 00o*a .oo

* . . 000000 0o 0 0 o* ** 0 0 00 00 0 0 0 0 0 **.... ....../ox o o o o o.. .. 0.000 X 0.. .x a o x o

* . . ..OX 0000 ...... . .

* . 00 0 0. - - * .-- 0 * 0 0 o x x 0 U * .

0 00 0 0 0 0 0.... 0 00o X Do 0..........O 0 X 0 * . * - - - - .* * 0 K 00 o X 0oO 0. . . *. - .- .- .

, 0 * 0 0 * 0 0 0... o 0 . * 0...*.**...*.*. ....O 0 * * 0 0 0 0 0 0 0 0 . 0........

* 0 0 0 0 0 0 0 0 0 0

* * * * * 0 . .- -O . * .... . 0 .0 u U

* 0 0 0 0 0 0 0 0

* 0 0 0 0 0 0 * 0 0

. . . .0. x. o~tO... 0

. . *0 * 0 0 .

O 0 * xxoo o* . . L X X O O O.

*. . . o O o o 0 o.

* . . .x x o oa

. . /a x x o o o .

O ~ 0 0U0 * 0.0. . . { o x x . o o

* . . o u x a oo..* . x x x o.ooo

. . I x a x x x x o l

:. . . a x o X a xol.0 UKK0 0 0

.0 * * OKO0 x

*. . .X X O K.O /-. . UXi~* ** XX 0

* , . O x X 0 X O X/ . .O * * * a a oo q 0..

* . . 0 *9 0 o . . .'O . . ..

0

23262599aII1 2

1 4Ir161S

O.

I.__ -f-# - -* -§________----------- -- - - - - - ---- +-- #--*___- -_- -_- - -_--_-_-_-_-

1 3 5 7 9 It 13 15 17 19 21 23 25 27 29 31 .3 35 37 39 41 43

TRIP

SYMB3OL

...... 0.0000000 -ti tz o o0.5065702 -

SP TO cse ro

0 .5*557021 .51 . ?I1 05

sy zu0

XXXXXX .15197105 -a*t-au 2.5328508 -

SPT

2.53285083.0394209

FIGURE 5.3-38CAPE FEAR ESTUARY

PLOT OF LARVAL OENStTlES OVER TIME AND DISTANCE UPSTReAMEPPECIEl-CROAKER bEPnioTTOM

CCNTYCR PLOT OF STATOTRIP

U'I

a,

20

P..'4

STAT

44 443 442 *41 f99 434 +33 +32 +31 +35 +36 437 f99 427 +24 +2 1 *22 +23 426 +

99 411 412 413 +14 417 +

56 t1 5

X X X . 0 X *X X X . a e

X X X . .0 0 .. XX*.

x x . . o~x . x x .1

0 X X a a X X X X XX i

O X at o o xX XX..o x Mx 0 x 0 x " 4

o X 0o o o o X Xj a .o X/ X o X o X . _t0

o a X X X X o o Xr...o vo a X X o . .

o b x x x o o & ..

. o as x a a o a

* 4

0.* 4

* 0

* 4

* .* a* 4

* 4

* .* 4

. .4 . . 4

* . .0 .

a A A 6 * 0

. 4 4 a 4 0

. 4 4 4 S X

. 4 4 4 o 8 04 a 4 4 * 0

. 4 4 4 4 0* a 4 . a *

* .. 4 a 0* * * * a 0

* 4 4 * a 4 a 4

* 4 0 4 4 4 a *

* 4 5 * * 0 4 0

x

x

x

x

x a 0x

X X X XX

x x 0 x x x x 0

x x 0 x x x a x

x x 0 x x x x 0

x x 0 0 x

x x x

x x x x x x x 0 0 x

0 0 0 0 X o 0 e

x x x x x x a 0

x x

0 0 X X X 0 0

X X X X X X 0

x x x a x x x 0

0 a X 0 0

a a x a 0

0 x x x x x

0 0 x

0 x

0 x 0 x0

a A 0 0 a x 0

0000

L - __- ,__ -__ -_ - ,_ - -_ -_ -__ +_- - -- ,-_ +-- _. +_ +___ +-_ -- f

a 3 5 7 9 I1 13 15 17 19 21 23 25- 27 29 31 33 35 37 39 41 43

TRIP

S YUH0L

...... O.OOOOOOQ -000000 0.5839469 -

CRK SYMBOL

xxxxxx 5.755840a -*ESS"N 2.9197347 -

0O 5e394691.7518408

CRK

2.91973473.5036816

II


PLOT OF LARVAL DEtSITIES OVER TIVE AND DISTANCE UPSTREAMSPECI ES-CROAKER DEPTH-SURFACE

CONTOUR PLOT CF STAT*TRIP

k-J I

I1

STAT

44 +43 442 +41 4"99 +34 433 432 +31 +35 +36 +37 4

Bz 95 +0 27 +- 24 +<, 21 4"-22 4' 23 +

26 +25 +99 +11 *12 +13 +14 +17 416 +1 5 1

U 0 o . . .0 o.o 0 a 0 0 0 0 .o a . 0 . 0 0 0n o . . . 0

O 0* 0

* 0

* 01* .100

0 :

*ol

. 0

0. .00.00

0

0 000.a0 0 00. o

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* * * * 0

O 0 . . .

0 0 0. .

O 0 0 0 0

. a . 0 .

. . . . .

. . . . .

. . . 0 . 0

. . . 0 . .

O . . . . .

O 0 0 0 0 0 0 0 0

O0 0 0 0a 0 0 0 0

* a 0 0 0 : 0 0 0

O 0 0 0

O 0 0 0

O 0 0 0

* 0 0 �

* 0 0 0

O 0 0 0

O 0 0

O 0 0 �O 0 0 0

O 0 0 0

* 0 0 0

0000

o 0 0 . o . .

O 0 0 0 0 o 0 0 0

0 a . .0 a . 0

0 0 0 0 0 0 0 0 0 0

O 0 0 0 0 0 0 0 0 a

O * 0 0 0 0 0 0 0 6

O 0 0 0 0 0 0 0 0 0

*0 0 0 0 0 0 0 0 0

O 0 0 0 0 0 0 a 0 0

O 0 0 00 .00 0 0 o _o 0 00

o 0 0 X0.O X00 0 0 x o *o 00 a 0 x o 0 0 x 0O 0 0 00.0 0..0 0 a 00 00 0.

O00 0 0 00.O a 0 0000.

o o 0 000o0o 0O 0 0 aOU 0x a

a o 0 o .. oO0 0 0 0 0 00

o o . 0 o o o . .* . 0 a 0 o . .O 0 0 a 0 X 0

* 0 0 000 00 0

. 0 0 . 0 .

O o 0 .0 u .0 . 0

0

O00

00*0

00.0

0*0

a00

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0.0

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TRIP

SYMHtL CRK SYMBOL CRKO.COOOOOO - 0.5039469

I1otmoI) o. 5e39469 - I.r! I8408XXXKXx 1-F518400 - 2.919134?massam 2.99934.7 - 3.50.36861


PLOT OF LARVAL DEKSITtES OVER TIHE AND OISTANCE UPSTREAMSPECIES-MENMADEN DEPTH-BOTTOM

COITOUR PLOT CF STAT*OTIP

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TRIP

SYMBUL MEN SYMBOL MEN

.....0 . t.0000000 - 0.6131614000000 0.61'1614 - I.e354643

XXXXXX 1.8394843 - 3*0e580r2mammas 3.065no72 - 3.6789686

FIGURE 5.3-41CAPE FEAR ESTIJARY

PLOT OF LARVAL DEkSITIES OVER TIME AND DISTANCE UPSIREAMIPECIES-MENHADEN DEPTHSURFACE

CCNTGUR PLOT OF SIAT*TRIP

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CAPE FEAR ESIUARYPLOT OF LARVAL DENSITIES OVER TIME. AND DISTANCE

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SYMBOL FLN

.*..... 0.000000 -000000 0.423798 -

0.4237981.271394

SYMBOL

xxxxxx 1.271394 -*"omma 2.118990 -

2- 1 189902.542788A



PLOT OF LARVAL DENSITIES OVER TIME AND DISTANCE UPSTREAMSPECIESFI.OUNDER DEMTH-SURFACE

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SYMBOL FLN SYMOOL FLN

...--. 0.000000 - 0-423798000000 0.423798 - 1.271394

X1CXXXX 1.271394 - 2.18990*Numea 2.118990 - 2.542788


PLOT OF LARVAL DENSITIES OVER TIME AND DISTANCE UPSTREAMSPECIES-SIRlMP DEPtH"BO1TOM

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SYMBOL S HR

xxxxxx 1.3094302 - 2.1823a36aisams 2.1823836 - 2.6188604

FIGURE 5.3-45CAPF FEAR ESTUARY

PLOT OF LARVAL DENSITIES OVER lIME.AND DISTANCE UPSIREAMSpEciEs-SHRiMP DEPTHWSURFACECONICUR PLOT OF STAT*TRIP

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SYMHBOL S HR SYMBOL SHR

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XXXXX X I.3094302 - 2.1823836ESSnXR 2.1823836 - 2.6188604

CAPE FEAR ESIUARYFIGURE 5.3-46 PLOT OF LARVAL DENSITIES OVER TIME AND DISTANCE UPSIHEAM4

SPECIES-ANCHOVY DEPTH-BOTTOM

COJNTOUR PLOT OF S1AT#TRip

STAT

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PLOT OF LARVAL DENSITIES OVER TIME AND DISTANCE UPSTREAMSPECIES-ANCHOVY DEPT"-SURFACE

CGNTOUR PLOT GF STAT*TRIP

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44 443 042 441 199 434 a33 f32 t31 435 *36 4

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SYMBOL ANC SYMBOL ANC...... .0.0000000 - 0.7111347ocoooo 0.7111347 - 2.1334042

Xxxxxx 2.1334042 - 3.5556737"among 3.555673? - 4.2668C85

CAPE FEAR ESTIUARYFIGURE 5.3-48 PLOT OF LARVAL DENSITIES OVER TIME AND DISTANCE UPSTREAM

SPECIES-TROUT DEPTH-BOTTOMCONTOUR PLOT OF SIATOTRIP

z

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S YMBOL TRT S SMDBL

0. 0000000 - 0.4z220790noI(o 0.42270?9 - 1.2 81 236

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PLOT OF LARVAL OFNSITI1S OVER 1IIFE AND DISTANCE UPSTREAMSPECIES-TROUT DEPTH-SUR FACE

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__ …_ …_ … _ … __ I_ _ + _ _ +-_ +- + * + * * … +_ *- +…* + - -t- - ---1 3 5 7 9 II 13 15 I7 19 21 23 25 .27 29 31 33 35 37 39 41 43

TRIP

SYMHOL IRT SYMMBOL 7RT

... &.. 0.0000000 - 0.422707900000c 0.4227079 - 1.2(81236

X)XXgXXX 1.2611236 - 2. 1135 393*uuuaa 2.1135393 - 2.5362472

Table 5.3-11 Regression analysis of trends in the abundance of selectedspecies of larvae at three river stations and in entrainment.

RIVER 1974-1978 (Stations 21, 24, and 25)

Mean Squares

Species

Spot

Croaker

Menhaden

Flounder

Brown Shrimp

Pink & WhiteShrimp+

Anchovy

SeAtrout

Trend

0.13156**

0.01690

0.00007

0.07834**

0. 43731**

0.01634

0.15719**

0.00168

% Change/Yr.

+30

+10

+1

+23

-49

+23

+50

+4

Deviation

0.08219**

0.02185*

0.00802

0.01026

0.01282

0.00080-

0.01339

0.01574

Error

0.00926

0.00654

0.01678

0.00777

0.04101

0.01034

0.00576

0.01043

Relati-teStd. Dev.

215

20

35

23

;9

26

19

27

ENTRAINMENT 1975-1978

Mean Squares

Species

Spot

Croaker

Menhaden

Flounder

Brown Shrimp

Pink & WhiteShrimp

Anchovy

Seatrout

Trend

0.00009

0.04836*

0.00323

0.02309**

0.18570**

0. 13626**

0.00002

0.01850

% Change/Yr.

-1

-20

-6

+17

-36

+46

0

-13

Deviation

0.04638*

0.09262**

0.01080

0.00077

0.03292

0. 15192**

0.09822**

0.05769**

Error

0.00962

0.00708

0.01724

0. 00259

0.02348

0.00649

0.01447

0.00586

RelativeStd. Dev.

_ )

21

35

11

.-~

32

u

* Significance level = 0.05** Significance level = 0.01+ No data for 1974

5-138

considered individually. In fact, densities of adult white shrimp

were observed to decline along the North Carolina Coast-in 1977 and

1978, and also were observed to decline in the CFE in 1977 and 1978

(CFS, Vols IX, XV). Entrainment densities during the years 1974-78

generally decreased except for flounder and pink and white shrimp.

The upward trends in river densities ranged from 1% per year (menhaden)

to 30% per year (spot). Brown shrimp river densities decreased 29% per

year. Entrainment density decreases were observed from 0% per year

(anchovies) to 11% per year (croaker). Flounder entrainment increased

8% per year and pink and white shrimp entrainment increased 21% per year.

Statistical analysis for each species suggests that some of these trends

can be explained in terms of the year-to-year fluctuations in abundance

or to the random sampling or both, but the weight of the combined evidence

clearly suggests a healthy estuary with no increases in plant entrainment

impact.

The BSEP began to withdraw water from the estuary in January 1974 and

the typical flows associated with two unit operation were observed from

1976-1978.* Of particular interest during this period were the densities

measured for anchovies. This species spends its entire life in and near

the CFE and would be impacted continuously from spawning to adulthood.

Yet the species increased significantly in abundance--by 23% per year--

while the average change in entrainment density was nil.

Trend lines, including 95% confidence interval estimates of the true

population densities, are plotted in Figure 5.3-50. In the trend

analysis, data from three stations in the vicinity of the intake

canal were combined to form the river data set (CFS, Vol. VII).

Entrainment sampling in the discharge canal for the same periods formed

the entrainment data set. Differences among years were partitioned into

a trend component proportional to the size of the linear increase (or

decrease) and a deviation component proportional to the size of the

year-to-year fluctuations around the trend line. The error component

*See Figure 3.2-1, which shows actual historical flows and comparesthem with Flow Minimization simulated to long-cerm full flow.

5-109

FIGURE 5.3.50 COMPARISON OF TRENDS IN RIVER LARVAL AND ENTRAINMENT DENSITIEs

SPOT

2.0-

1.3-

1.0-

0.5-

* 3.0

* 2.5

-2.0

*1.S

-

A

4f.

zMAa0

0.A

Cl

Cl

ClU,

z0

lw

W.tj - . .u

CROAKER

1.5. 2.5

1.0 * -2.0

0.0'- 1.0

MENHADEN

1.0 2.0

0.5 .*1.5

'0.. .1.0

z

z3z'4

F,

00

zU'-4

;

FLOUNDER

1.0-

0.5-

-2.0

1.5

I.:U AlI

i I . I

74 75 76 77 787 i I I7 5 76 7 7 78

YEAR

- ! 10

FIGURE 5.3-50 (CONT.)

m"z-4

-4

F-00

z-4

4.

74 75 76 77 78 75 76 77 78

YEAR

5-111

used to judge the significance of the first two was computed from the

discrepancy between sampling periods within years. The percent change

per year is calculated from the slope of the trend line, and the

relative standard deviation is the square root of the error mean

square expressed as % of average density. The latter is included

because it represents the intrinsic random error encountered with

each species. The logarithm of the densities was analyzed throughout.

A significant trend component with no significant deviations suggests

a simple increase (or decrease) over the indicated period. Significant

deviations on the other hand indicate that the year-to-year fluctuations

cannot be described simply by the linear trends and may be associated

with year-to-year fluctuations in the overriding environmental factors

such as temperature and salinity. No significant trend or deviation

implies a relatively constant level of abundance in the species.

Population densities of larval species in the CFE vary over the short

term due to factors such as vertical migration patterns, tidal influences

and changes, and phototactic responses, to list a few. In addition to

the short term variability in the larval populations as discussed in

Sections 5.3.2.1-5.3.2.6, differences from year to year arise from such

factors as the size of the spawning populations, the hydrographic

condition of the estuary (salinity and temperature) during the recruit-

ment season, and the ocean currents which the larvae must use to

migrate to the estuary. Over a long enough period, say twenty years,

one would expect to see a great deal of variability from year to year,

but a trend which shows no significant increase or decrease as long

as estuarine conditions do not deteriorate. Over a four- or five-year

period one would expect to see trends in abundance which both increase

and decrease, depending on species, given no more than natural

perturbations in environmental conditions. For example, the decrease

in brown shrimp is clearly attributable to the cold winter of 1977

and the high freshwater flows in 1978 since this trend was observed in

other North Carolina estuaries.

In 1976 testimony, EPA witnesses (wich whom the EPA Regional

Administrator agreed) estimated entrainment losses of larval fishes

in the range of 25% to 99.9%, with most estimated at 60X-70%*. Impacts

of this size would almost certainly have produced negative trends in

larval abundance and have been detected in the data set accrued thus

far. Trends of 8% per year were detected in flounder with an intrinsic

random error of 12%, while trends of 29% per year were also detected in

brown shrimp with an intrinsic error of 59%, shrimp being the most

variable species. On balance, changes of the order of 25% per year

would have been seen if the changes were real.

5.4 Specific Data on Use of the CFS by Juveniles and Adults

5.4.1 Abundance, Seasonality, and Distribution

A summary of the seasonality of nekton in the CFE is presented in

Table 5.4-1. Additional details, by species, are given below.

Croaker - During the winter, juvenile (age 0) Atlantic croakers

appeared in the CFS trawl catches as early as January and juveniles

continued to enter the system through May. Growth in the juveniles

can be noted in the length frequency tables (CFS Vol. XIV, Tables

172-176, pp. 448-452 and Vol. XV, Fig. 17a-c, pp. 211-213) indicating

that croaker remain in the estuary during their first year of life.

Peak numbers of croakers were caught in the spring when both juveniles

and yearlings were present (CFS, Vol. XIV, Table 86b, p. 232). They

were primarily found in the deeper areas of the river (ship channel and

intake canal) and less frequently in the more shallow areas of the

river (CFS, Vol. XIV, Table 88c, pp. 271-272 and Vol. XIII, Table 5,

p. 39). By summer, most of the yearlings (90-150 mm SL) had left the

system, presumably migrating northward (CFS, Vol. XIV, p. 50). Tagging

studies have shown that croakers tagged in the CFE have moved in some

cases over 140 miles to the north (CFS, Vol. XIV, Table 118, p. 375).

In the fall, adult croakers (over 200 mm SL), probably migrating

south, are sporadically caught in the CFE. Adults migrate to

*See footnote, page 1-8, above.

3-113

Table 5.4-1 Seasonality of juveniles (age 0) of major species in CFE

Jan. Feb. Mar. Apr. j Jun. Jul. Aug. Sep. Oct. Nov. Dec.

Croaker

Spot

Weakf [sht

Menhadien0

I ilFiuund er

Au Micovy

Brown shrimp

WhiLte shrimp

'iunk shrimp

Stardrumui

x N

x

A. -

>

__

A

> x

x

x~

x-

X = Time of f irst catches

> = rime of disjippearanee or to overwintering

--- - -. -A Sporaldic CaiLCIeS

offshore spawning grounds in the fall and early winter. During the

winter, adults have occasionally been found in shallow water off Oak

Island. They may have been forced from the north by extreme environ-

mental conditions as occurred in 1976. Otherwise, varying numbers of

adult croakers were captured in the nearshore ocean area (CFS, Vol. XV,

Fig. 34c, p. 121).

Spot - Early juvenile spot generally appear in the CFE from February

to May (CFS, Vol. XIV, Table 162-166, pp. 438-442). They remain in

the more shallow areas of the estuary through their first year. Spot

dominated the fall and winter catches as yearlings as they moved into

deeper waters of the lower estuary or offshore to overwinter (CFS,

Vol. XIV, Table 88d, pp. 273-274 and Tables 162-166, pp. 438-442).

Overwintering yearlings remain in the estuary through the spring before

migrating out of the sampling area. Tagging data indicate that these

spot, in some cases, move up the North Carolina coast (CFS, Vol. XIV,

Table 118, p. 375). Near the end of their second year of life, spot

move offshore to spawn. Yearlings are found in the nearshore ocean

area in late fall to early winter. Older fish occupy the same nearshore

area from October through December.

Weakfish (Trout) - Juvenile (age 0) weakfish appeared in the CFE between

May or June and September, with peak catches recorded during July and

August (CFS, Vol. XIV, Table 87a, p. 253). In 1976, fishes from two

separate spawnings could be distinguished, with one group appearing in

May and the other in September (CFS, Vol. XIV, Table 150, p. 426).

Trawl catches dropped off rapidly in September as the majority of these

weakfish moved out of the lower estuary to a few miles offshore. The

one exception to this trend occurred in January 1976 when a large number

of larger fish (still age 0) (127-203 mm) were collected during an

extreme cold period (CFS, Vol. XIV, Table 150, p. 426). Weakfish over a

year old were only sporadically caught, usually during the fall.

Menhaden - Age 0 menhaden utilize the lower saline areas upriver

during the spring, moving downstream with increased river flow.

5-115

Yearlings (-90-126 mm SL) predominate throughout the river from

November to April (CFS, Vol. XIV, Tables 142-146, pp. 413-422).

Menhaden of all sizes are found in the ocean during the summer months.

Age 2 or older fish return to the lower estuary in November, dominating

the gill net catches, and are found at leas. to Snows Cut. Tagging

studies show that menhaden tagged in the CFE move as far as 180 miles to

the north and 94 miles to the south (CFS, Vol. XIV, Table 118, p. 375)

during various months of the year.

Mullet - Mullet are schooling pelagic fish that are usually found in

the upper portion of the water column. Nekton sampling produced fewer

than 1800 organisms of both species (white and striped) combined for

all six years of sampling, but this is probably a low estimate of

relative abundance (IFS, Vol XV, Table 20, p. 75). Mullet are good

swimmers and are usually able to outswim the trawls to avoid capture.

Around 40X of the mullet that were collected were larger fish collected

in gill nets (CFS, Vol. XIV, Table 85a, p. 226). Tagging studies

reveal that mullet may move as far as 140 miles to the north of the

Cape Fear.

Flounder - The estuaries of North Carolina act as vital nursery areas

for the genus ParalichthYs (Poole 1966; Powell and Schwartz 1977). The

simmer flounder (P. dentatus) and the southern flounder (P. lethostigma)

are the main species of commercially important flounder present in the

CFE. Age 0 (10-40 mm SL) flounder appear in the Cape Fear River between

March and May (CFS, Vol. XIV, Table 177-186, pp. 453-462). Juveniles

penetrate well into freshwater past the salt front, and gradually move

downstream during the fall. Flounder, especially P. lethostigna,

probably remain in the estuary until they reach at least age 3 when they

migrate offshore to spawn. P. dentatug spawns around 25-30 miles offshore

while P. lethostigma probably spawns closer to shore.

Bay Anchovy - Age 0 bay anchovies (20-30 mm SL) appeared in the CFE

primarily from August to October (CFS, Vol. XIV, Table 132-136,

-1

pp. 403-407). The appearance of young bay anchovies as late as April

indicated an extended spawning period, perhaps through September. Bay

anchovies were taken in every sampling month indicating they remained

in or near the estuary their entire life. Length frequency tables show

only a single age class prevailed. Because of their small size, none

were tagged.

Shrimp - There are three species of commercially important penaeid shrimp

in the Cape Fear estuary: brown, pink, and white. They are short-lived

species and rarely exceed a year in age. Brown shrimp enter the estuary

as postlarvae during the winter and early spring and grow large enough

to be collected in trawls by early June. They reach commercial size by

July and are harvested by commercial shrimp fishermen as they migrate

through the lower estuary and nearshore ocean toward the offshore

spawning grounds. A few of the late-spawned (smaller) brown shrimp

remain in the estuary through November, although the bulk have left even

the nearshore ocean area by September (CFS, Vols. XIV, XIVa-e, XV).

White shrimp is usually the most abundant and commercially important of

the three species in the CFE. They begin to enter the estuary in May

and by July are large enough to be captured in trawls anywhere north of

Snows Cut where they move from creeks and marshes into the lower estuary

as they grow, usually being pushed out of the shallows and eventually

the entire estuary as water temperatures drop in late fall and early

winter. During mild winters a portion of the population (probably those

spawned late in the season) overwinter in deeper portions of the estuary

(CFS, Vol. XIV, Table 25, p. 136). Pink shrimp development parallels

that of white shrimp, but they are usually less abundant and in high

salinity areas (CFS, Vol. XIV, p. 29). However, during 1977 and 1978

pink shrimp were more abundant in the CFE nursery areas than were

white shrimp.

Shrimp are known to have a wide ranging distribution. The three species

of penaeid shrimp range north to Cape Hatteras and south to the Gulf of

Mexico. Thirty-four of the shrimp tagged in the Cape Fear estuary were

recaptured after moving at least 47 miles to the south and three were

recaptured after moving over 280 miles to the south (CFS, Vol. XIV,

5-117

Table 117, p. 374). In all probability, shrimp leaving the Cape Fear

estuary mix with shrimp migrating from a number of different estuaries

in South Carolina and Georgia before moving to the offshore spawning

ground.

Stardrum - Young-of-the-year (age 0) stardrum (Stellifer lanceolatus)

first begin to appear in the catch in July and August (CFS, Vol. XIV,

Tables 187-191, pp. 463-467) and continue to enter the catch through

October and November. Stardrum exhibited a more limited distribution

in the CFE, showing a clear preference for the river channel from Buoy

27 south. Nekton studies show consistently higher CPUE's in the ship

channel with the center of distribution in the vicinity of Buoy 19-27

(relatively close to the BSEP intake canal) (CFS, Vol. XV, Table 34b,

pp. 119-120). Catches were low in the ocean and even lower in the shoal

areas and intake canal stations. Seasonally, stardrum were captured in

all months with variable peaks of abundance (CFS, Vol. XIV, Table 87d,

p. 263). Stardrum are a short-lived species probably living less than

two years. The absence of older individuals suggests a high mortality

rate after spawning (CFS, Vol. XIV, Tables 187-191, pp. 463-467). This

species is of interest because of its close proximity to the intake

canal area.

5.4.2 Fluctuations in Abundance of Juveniles and Adults

5.4.2.1 Introduction

A variety of juvenile and adult data were used to examine community

structure, diversity, population fluctuations, and trends in the

CFE.

During the period 1952-1962, the Federal Paper Company (Acme, North

Carolina) sponsored nekton trawling programs in the Cape Fear estuary

(hereafter referred to as Federal Paper data). Their stations were

S-118

situated both in the main stem of the estuary and in Dditchman Creek.

Additional data for the Cape Fear estuary used in the analyses

includes the CFS trawling data (CFS, Vols. XIV, XIVa-e, and XV) and

encompassed the dredged ship channel, BSEP intake canal, main stem

shoals, Carolina Beach Inlet, and ocean area near the BSEP thermal

discharge site (hereafter referred to as CFS data). These data

(CFS, Vol. XVI, Appendix A), along with others, form a body of

information on adult and juvenile abundance within the Cape Fear

estuary.

In addition, an annual trawling program conducted by Dr. W. W. Hassler

(unpublished) in Albemarle Sound, North Carolina, provides a 23-year

data base of catch per effort of nekton (hereafter referred to as

Albemarle data). With data such as the Federal Paper and Albemarle

data sets, fluctuations in abundance can be observed over the long

term. As ancillary information, commercial fisheries' statistics were

compiled statewide and by each fishing district to assist in defining

population fluctuations. All of these data are used to assess the

significance of the fluctuations in abundance of juveniles and adults

in the CFE since 1973.

5.4.2.2 Penaeid Shrimp

This section discusses fluctuations of shrimp in the Cape Fear and South

Atlantic Bight and describes recent research on the effects of salinity

and temperature on shrimp production.*

*It should be noted that the harvests of commercial species otherthan shrimp have also been found to be correlated with salinity andtemperature fluctuations in their environment. Sutcliffe (1972, 1973)found increased catches of lobster to be associated with high riverflow in the Gulf of Lawrence. In England, rainfall was found to affectpopulation size of Crangon crangon (Driver 1976). Finally, Kobylinskiand Sheridan (1979) studied the effect of temperature and rainfall onpopulation fluctuations of spot and croaker in the Gulf of Mexico.They concluded that temperature was a significant determinant of long-term abundance of spot.

5- 119

The commercial fisheries' landings ate- used to exi3mine.possible causes

of recent declines in penaeid catches which ha-we caused concern to state

officials not only in North Carolina but in South Carolina and Georgia

as well. Interestingly, the North Carolina Division of Marine Fisheries

(DMF) (Hunt et al., 1978) has been working with the University of North

Carolina, Chapel Hill, to develop regression models capable of predicting

shrimp landings. At first 11 environmental variables were examined, but

it was found that the major variables were temperature and salinity

and interactions between them.

Using the shrimp model developed by the University of North Carolina,

Chapel Hill, the DMF staff was able to predict the recent shrimp

declines.** They stated:

"Juvenile sampling, environmental conditions, and theUniversity of North Carolina, Chapel Hill, model allsuggest an abnormally low brown shrimp crop, probablyaround one million pounds (heads off) or about 60%below the 1967-1977 average of 3.8 million pounds. Thisin itself might not be too serious; however the problemhas been compounded by the past two extremely severewinters. Both winters have resulted in near total "wipe-outs" of the overwintering pink shrimp crops, with totallandings for spring 1977 of less than 30,000 pounds andreported landings for the spring 1978 falling below1977 thus far. Since the major portion of the pinkshrimp harvest is usually landed in the spring, landingsof pink shrimp cannot be expected to be above about250,000 pounds this year, although last year's landingswere,340,000 pounds. This figure is considered excep-tionally high and cannot be expected this year, based onpast data. White shrimp, which are the most sensitiveto cold, cannot even be considered in total landings thisyear. Both South Carolina and Georgia report considerableconcern about the white shrimp crop, and Georgia isconsidering requesting an extension on their shrimp resourcedisaster loans. When these states are concerned abouttheir white shrimp crop, North Carolina's expected landingsof this species will be negligible. This is borne out bylast year's landings which totaled only about 5,000 poundsin North Carolina."

**The actual brown shrimp catches in 1978, once full datawere av2 _' : ha- ye---r, -h. :,an predfi ted by theshrimp model.

3-120

In contrast, the approach used here is not predictive; rather, it uses

empirical data to correlate temperature with observed shrimp catches.

An analysis of shrimp changes is complicated since the three commercial

penaeid species (brown, white, and pink shrimp) need to be analyzed

separately. Each species has a distinct abundance trend and appears to

exhibit a different susceptibility and response to environmental

variables. Furthermore, the changes that have taken place in shrimp

densities appear to have occurred over a broad geographical area ranging

from North Carolina to the east coast of Florida. This means that under-

standing shrimp fluctuations requires a full data base for this broad

region encompassing the South Atlantic shrimp fishery. First of all,

to show general penaeid shrimp fluctuations, data were compiled

(Figure 5.4-1) for the three Penaeus species together.

Throughout most of the South Atlantic region shrimp catches declined in

1977 and 1978 as indicated for the Cape Fear. However, in 1978, data

for the southern district of North Carolina showed a recovery. Catches

have typically been variable, but two sets of data for Dutchman Creek

(CFE) suggest that shrimp densities in that area have not changed greatly

since the 1950s.

Brown Shrimp

Commercial landings of brown shrimp in the South Atlantic states

(North Carolina, South Carolina, Georgia, and Florida) have been variable

(see Figure 5.4-2), and there have not been any large unidirectional

upward or downward trends. Given the observation that these landings

data do not match each other precisely, the four curves nevertheless

appear related. Furthermore, the same general variability is noted in

the Cape Fear data of Schwartz, although this latter data base suggests

that a recent increase in brown shrimp densities may be occurring.

Correlation analysis of annual CPUE with mean monthly temperatures

reveals no significant relationship between Cape Fear brown shrimp annual

CPUE and mean temperature during any month. However, decreased salini:y

5-12I

fivru 6.4-1 Compilation of coummarcial lawidnLs and cawch/affort data basesPunafld shrimp (AJI spacles)

__ I V)"

' Uks Icit scali for ScIhwartz. Uuuv 4U. Dutclumul Ctuk. Oteias use dUht scale." All wpcls combim"id, woiuldas woe1seacts-0.

K),

mu.

6OOGIWA p.

40.C. STA I fWI)E , __2 * *. .,. *. . >

SUTII CAHOLIMA .c Ct.lHI.

N.C. SOU1h rw

IxglauCT

'..ff -.. \

MC. '4

SIUTOIAN

CRIEIADsail

I.

: -I

_K4)

G

z

2

z

IL

J'4 i

lo 6

w

uiUY 46-

itt.

A ,

A'&I

''IVUU ICIMAN

CHttKIfEUDIA6. r"aC)

II

q

it,

I'I

.4 . ' I .. .'' I .?

SCIIWAUIIZ

CFS

a aa to a. . . . ., . .4 . . ,

'9

.. I

CAPE FEAR ESTUARY MCMUE)

IF

00 'n

aa00

INI

COMMERICIAL LANOINOS (POWUNS; HEADS-OFF)


I

in winter months seems to have an adverse effect on the brown shrimp

catch in the CFE during the same year. The effect of temperature on

brown shrimp production has been well documented. For example,

Venkataramiah et al., (1977) provided extensive data on the physiological

responses to lowered temperatures of brown shrimp. Saint Amant et al.,

(1962) showed penaeid shrimp populations to be extremely responsive to

certain unstable hydrological conditions. High river stages, resulting

in lowered salinities and sudden temperature changes, could severely

alter abundance of the species. Gaidry and White (1973) in brown shrimp

studies conducted along the Louisiana coast from 1969 through 1972

showed a clear relationship between brown shrimp production and higher

salinities and favorable temperatures. In contrast, lower shrimp produc-

tion aligned with adverse hydrological conditions. According to

Barrett and Gillespie (1973) the number of hours water temperatures

remain below 200C after the first week in April has a significant

influence on subsequent production levels. Studying 1973 flood conditions

in Louisiana estuaries, White (1975) found that salinity and temperature

conditions that prevailed following the arrival of postlarval brown shrimp

had an adverse effect on brown shrimp growth, dispersal, and survival.

This resulted in a considerable loss to the shrimping industry (White 1975).

Finally, the North Carolina Division of Marine Fisheries found (Hunt

et al., 1978) that salinity and temperature conditions during April and

Hay in the brown shrimp nursery areas in Pamlico Sound are the most

important parameters affecting brown shrimp harvest. Brown shrimp growth

rates decrease and mortality rates increase at low salinities and tempera-

tures. Ten parts per thousand salinity and 200C temperature are found

to be threshold levels below which harvest is poor and above whichharvest is good. Using the early April salinity and temperature averagevalues, in conjunction with estimated values for these parameters through

May, the Division of Marine Fisheries used their model to successfully

predict brown shrimp harvest in the Pamlico Sound for a given year at the

beginning of that year.

5-124

Pink Shrimp

Pink shrimp show a marked increase recently in Florida (east coast) and

South Carolina landings (Figure 5.4-3). This is similar to the trend

seen in the Cape Fear, but the catches there were low and never reached

one individual per trawl effort and.so no correlation analysis was

performed. North Carolina evidenced a decline in pink shrimp landings

since 1974 that may indicate a southern migration of these shrimp in

colder winters.

White Shrimp

The white shrimp (Figure 5.4-4) show a general decline for all four states.

The decline is steepest for North Carolina and becomes less steep further

south:

WHITE SHRIMP ANNUAL CATCHES% Change Since 1973

YEAR NC SCHWARTZ (CFS) SC GA FL

1974 -89.1 - 5.3 -18.1 -23.9 -11.11975 -65.0 -13.0 - 1.0 -11.7 - 9.01976 -78.6 -30.2 -10.4 -22.9 - 1.31977 -99.5 -92.6 -89.8 -60.8 -43.11978 -97.1 -93.1 -61.8 -75.1 -13.9

This trend seems to indicate a relationship between white shrimp

abundance and temperature. The best readily available measure of cold

temperatures is the number of days that minimum air temperature was

below 00C (Figure 5.4-5). The stations used were: for North Carolina -

Cape Hatteras; for South Carolina - Charleston; for Georgia - Savannah;

for eastern Florida - Daytona Beach. Correlations between landings and

this variable are:

North Carolina -. 4583South Carolina -. 7897**Georgia -. 6601*Florida -. 6980*

*-sig. a = 0.05 (one-sided test)**-sig. a = 0.01 (one-sided test)

5-125

Figure 5.4-3 Annual Comffwcial LandingsPINK SHRIMP

.RONTW CAROUNASCUT.)* CdROUPI

-*-GE0441A........ EASt F.OR410A

\/I

7I 0

ZIL.9

50

a

z

*U

too Z

SOI

(AZ

Z

.A. I

,. ,

* I.- I- " -.. a.

,1N

/ i

* / /* I

. .I

\ //

/ I

\ . i

975 S712 .97's *S7' S9 -S?7L *S?7 . .9.lU E 7S A

saj4m@ nqsa ft 2aim ;ofia*enqs

5-12 6

Figure 5.44 Annual Commercial Landing and CPUE for Cape Fear EstwaryWHITE SHRIMP

- NORTh CAROLUNA- -SCUT14 AROLINA

GEORGIA* EAST FlOR10

C FE

"IC

N-%-* .

1000

w

0m.a

4

a

UPw

w 100

w

CU

*.................. II-%.. ' '.

f.. \.. ,/

\* -

I ''I

-' cI

t

4

i4

I

. 5

-4II1

4, ,

x

<

!'

.Ilo ~. c4

,I I , I . , . I . , e

1S71 1972 1973 1974 1975 1976 I9?? 7 19?U% 1979*

E.A -t*onainqv are o~or~ict 'ondifns

Figure 5.4-5 Number of Days in which Air Temperature was less than 0C

NORTb CAROLINASOUTH CAROLINA

-- *-GEORGIA..... -- * EAST FFLORIOA

6

zAt4z

<I-

W

WI.Ca

0

z

11

60t

50-

"I

/

,e _ _ _ _\a

-I/

30 I-/

201

10

01971 1972 :973 1974 1975 1976 1977 197'

YEAR

5-1 3

The relationship is significant in the three southernmost states.

Since even this crude climatic indic tor is strongly correlated, it

appears that cold weather is one of {he variables influencing white shrimp

declines. The influence of environmental variables on shrimp was

discussed previously for brown shrimp. Studies by Farmer et al., (1978)

on white shrimp in South Carolina revealed a disappearance of white shrimp

from all sampling locations during periods of low water temperatures.

They stated that there appears to be a strong relationship between winter

water temperatures (especially during 1977) and the succeeding white

shrimp populations size in coastal waters during April through June. In

the Charleston area, air temperatures during the 1976-1977 winter were

well below normal, the winter being the most severe on record. This cold

weather and resulting cold water temperature drastically affected the

white shrimp population (Farmer et al., 1978). Shrimp mortalities were

confirmed in January and February (1977) when numerous dead white shrimp

washed ashore on local beaches. Farmer showed that white shrimp catch

data and winter temperatures between 1940 and 1970 indicate that severe

winter water temperatures affect not only the spring roe shrimp catch

but fall white shrimp landings as well.

5.4.2.3 Finfish

Community Structure in the Cape Fear

Detailed analysis of the Cape Fear nekton community including abundance

trends, species diversity and richness, seasonality, and distribution are

also found in CFS Vols. XIV and XV. The following is a summary of some

of those findings.

5-129

During the 1978 nekton monitoring program, seven species comprised 90.4%

of the overall catch (menhaden (53.3%), spot (11.6%), grey trout (9.1%),

spotted hake (6.9%), croaker (5.0%), stardrum (2.3%), and anchovy (2.2%)).

Thirteen of the top 15 species caught in 1978 were among the 15 listed

during 1973-1977 (CFS, Vol. XV, Table 28, p. 87). These data indicate

that the composition of the nekton has not undergone large changes since

the inception of the sampling program. Similarly, the diversity of the

community has not shown a decline during the study period. The number of

species caught each year varied between a low of 118 in 1973 to a high

of 141 in 1977 (CFS, Vol. XIV, p. 37).

The usefulness of community diversity information is seen in studies which

relate stress on a biological community to a decrease in diversity

(Bechtel and Copeland 1970; McErlean et al., 1973). Analysis of the

Cape Fear nekton data shows that diversity indices rose during 1973-1978

(CFS, Vol. XV, p. 287), as did the overall catch per unit effort (CFS,

Vol. XV, Figure 43, p. 291). These positive, regression lines for

diversity and overall catch per unit effort provide an estimator of

"health" in the total fish community.

Fluctuations in Finfish Populations

To quantify fluctuations in abundance of juveniles and adults, the

available data were subjected to trend analysis.. The first step in this

procedure is to depict the manner and direction in which densities of

representative species increase and decline each year. The abundance

fluctuations depicted by Schwartz (CFS, Vol. VX) represent the combined

nekton data for all gear types. Extracting data for only large trawl

collections (Figures 5.4-6 to 5.4-8), one can see that the trends as well

as the regression lines of annual CPUE against time show essentially

the same results. Note that for five of the nine species shown in

Figures 5.4-6 to 5.4-8 the slopes of the regression lines of annual CPUE

3-130

a.

az2aI%

Figure 5.44; Abundance fluctuations for juvenile and adult fishes in theCape Fear Estuary 1973 - 1978

Stellifer lanceolatus.160 (Star Drum)

140 A y -10.02x +104.15

120

100

40 /

I220 .

160

140

120

a,. 100

U: 80-

60

40

20

40 -LU

t 30

' 20-

10 -

Micropogonias undulatus(Croaker)

/

IA\y- 1. 1 6x +48.85

I'\

\

N

/ 1%/ '.4

- _

Lagodon rhomboides(Pinfish}

y -Q.94x '17.28

/ \\/ ' \7 // /

/ -_

// N.-_ - = - -

1 973 1974 1975

LARGE TRAWL COLLECTION

1976 1 977 1978

5 - 1 3 1

Figure 5.4-7 Abundance fluctuations for juvenile and adult fishes in theCape Fear Estuary 1973-1978

Brevoorti tyrunnus280 (Atlantic M nhdon

240 o 3!

X 200

, 160

120

80

40 '.

5.47x -40.07

100.

80

soMu

m0. . soU

i 40.c

C20.

s0LU

U 40la

a 30c

20

10

Lelostomus xanthurus(Spot)

I/I\II

// V1 '

/ vI/ \ 1

- 1.39x +37.72

Cynoscion regalis(Wuakfish/Gray Trout)

Ye 5.42x -3.D5

1973 1974 1975 1976 1977 1978

LARGE TRAWL COLLECTION

5-132

WJG.Q

laa:.R

Figure 5.4-8 Abundance Fluctualions for Juvenile and AdultFises in the Cape Fear Estuary 1973- 1978

Uro3hycis regius

40- (Spoted Hale)y-2.93x +1.25

30

20.

10

Wu.U

ul

U

4

Wa.

aCI4C

2

15

10

5

10

5-

Bairdlefla chrysoura(Silver P-rch)

yuO.32x +3.74

-, ~ .

:1.0

10

- -ft-

I

Anchoa mitchilli(Bay anchovy)

y-0.26x +4.61

_ - - - -_-- a,_ __

.1

50-

40-

Anchoa mitchilli(Bay anchovy)

SMALL TRAWL y- -1.84x +24.21

/ ^\IUJm 30-a.U

I 20-

4 10-

/ \/

//

1/

I - - - -I

I1973 1974 1975 1976 1977 1978

L: RGE TRAWL COLLECTION (EXCEPT AS NOTED)

5-133

are essentially zero, and what is observed is simply fluctuation about

a long-term average. For all of the nine species statistical testing

showed that none of the slopes of the regression lines were significantly

different from a zero slope. Preliminary evaluation of available

1979 nekton data indicates that the CPUE of these species has generally

increased substantially over 1978 CPUE.

Environmental variables that appear to be related to these abundance

changes are also discussed. Two variables believed to influence popula-

tions strongly are temperature and salinity. The wide spectrum of

temperatures that occurs during the year (and between years) in the

Cape Fear is believed to elicit a correspondingly wide variety of

responses from its resident and transient biota, the type and magnitude

of the response being species-and-life-stage specific. Temperature was

examined as one of the factors influencing population size, since this

relationship has been shown for species of importance in the Cape Fear

(CFS, Vol. XV, pp. 170-172). The nekton data confirmed the hypothesis

that the effects of natural events were significantly more far-reaching

and influential than operation of BSEP (CFS, Vol, XV, pp. 170-171). For

example, following the cool winter of 1973, CPUE values for nine of the

ten most common fishes were low (CFS, Vol. XV, Figures 7a, 7b, pp. 175-176).

During the warmer winter of 1974-1975, each of the CPUE values increased

only to drop again in response to the cold winters of 1976-1977 and

1977-1978. Of note is the observation that the CPUE of the cold-water

species, spotted hake, increased in the cold winter years of 1973, 1977,

and 1978.

A preliminary attempt was also made, using simple linear correlation

analysis, to determine the relationship between annual CPUE of various

fish populations in the Cape Fear and environmental conditions (tempera-

ture and freshwater flow) in the estuary. Although a number of signifcant

correlations were observed, it was realized that among other reasons, since

annual CPUE represents a mixture of year classes, some of the correlations

are likely to be spurious. Furthermore, biological interpretations of

5-134

the results become difficult since the fish have been subject to

environmental conditions of the previous year. Also, the results could

reflect movements into or out of the estuary or distributional shifts withi-

the estuary. The principal investigators hope to examine the influence

of environmental variables by extracting young-of-the-year catch data

to see whether the major Cape Fear populations have been responding to

changes in these variables. As a preliminary analysis regarding the

ability to detect an influence of BSEP operation against the existing

background noise of sampling and environmental variations, annual CPUE

and estimated YOY CPUE of fish were correlated with cooling water flow.

There were no significant negative correlations between cooling water

flow and either measure of CPUE. Spot and croaker, representative species

used in the fish population model, are discussed further in the following

sections.

Spot

Catches of spot have been examined for Dutchman Creek from two data sets

and for the mainstream of the Cape Fear estuary, Albemarle Sound, North

Carolina commercial fishery landings for the state overall, and for

individual fishing districts. These catches (Figure 5.4-9) confirm

the consensus of fishery biologists that high variability is a basic

characteristic of the species with mean catches between years varying

by over one order of magnitude. Interestingly, the catches are of a

cyclic nature peaking every three years in Dutchman Creek and every

three to four years in Albemarle Sound. A detailed analysis of the

Albemarle Sound data is presented in Section 6.0, CFS, Vol. XVI. The

data collected by Schwartz in the Cape Fear also show a cyclic pattern

but with a different frequency. In contrast, the North Carolina commercial

landings, both statewide and for the southern district, do not show

these cyclic patterns but do show high variability between years. What

this means is that the spot populations in the various areas that have

been sampled have not shown a unidirectional progression of increasing

or declining catches; rather, the catches have been oscillating about a

long-term mean. Of course, the fluctuations of spot might be attributed

zo responses to several different environmental variables and/or to

internal (i.e., density-dependent, population regulation, or other

factors).

,- 135

Figure5.4-9 ComPilation of commnercial lanidings and catch/effort data bases"Spot (Lelostomus xanthurus)

*Use left scale for Scluwartz, Albernarle Sound. Dutchman Creek. Others use right scale. HCAr,

NORTh

-J1

0*

DISTNM

CAAO""4P-:cf 1%

// \ /

/I41.-

a )

-Jk

.4

0

U

SCIOWARTZ

CFS

I

/

IIIIIIiII

OA

A'

I'

A

I'%I %I %I %I I'I 9'

II 9'% I/ - -.% I

\\I\\ j

AI/ \I/ . I

I.

CHEEK01AI1KflEA0 et ml

d IV 'I

I '-60 62 64 66 fe70 12 74 16

YE~ A"S

Croaker

An examination of the various data bases for croaker (Figure 5.4-10)

reveals high variability with changes between years of one order of

magnitude in some cases. Of note is the observation that density of

croaker during some years was markedly lower than the long-term average

with no apparent threat to the persistence of the species. This is shown

well by the long-term data base from Albemarle Sound which reveals a

history of high variability for croaker. Croaker data collected in the

Cape Fear main stem during the 1950s showed similar fluctuations as do

the recent data gathered for this species. Furthermore, these two data

sources indicate that Cape Fear croaker densities are not declining over

the long term but are fluctuating about a long-term average.

Commercial landings of croaker for. the state of North Carolina are also

variable but, in the past five years, record catches have been landed each

year; the statewide catch now approaching 20 million pounds per year.

Even if increased fishing effort offered a partial explanation for the

increased commercial catches, these catches cannot be attributed simpl,

to changes in effort (G. Nelson Johnson, NMFS, Personal Communication).

While the poundage recorded from the southern district has represented a

small percentage of the statewide landings for the past decade, the

recent increase in landings mentioned above is also observed in the

southern district. In other words, the fluctuations are similar but the

pounds landed differ.

In areas outside of the Cape Fear other scientists have reported fluctuatic

in croaker which were related to temperature. For example, Chao (1976)

felt that winter temperature probably was the most important factor

determining the success of a given year class of croaker. Furthermore,

Joseph (1972) stated that "a fortuitous set of circumstances in 1966

provided the most concrete evidence supporting the premise that year-

class strength may be related to temperatures in the nursery grounds."

He proceeded further to provide evidence that long-term temperature

trends have been related to population changes of the croaker.

;-137

Fiure 5.4-10 Compilation of commercial landings and catch/effort data bases'Croaker (Micropogonias undulatus)

10

*Use left scale for Schwartz. Albemarle Sound. Buoy 46. Dutchman Creek. Others use right scale.

K)~ NOfhII CAPIIONA 10

I,hi

co. D 2

A.

K)' AL

/ : A\!---O. CAROLINAA -I - -. J I

YEARS

5.4.3 Recreational and Commercial Significance of Cape Fear Nekton

Most of the representative important species which use the Cape Fear

estuary are used by man for commercial and recreational purposes. With

the exception of anchovies, each of these species is caught in the North

Carolina commercial fishery and many are also found in the South Atlantic

and Gulf of Mexico commercial fishery. Additionally, commercial catches

are reported in the Chesapeake and middle Atlantic regions for several

of these species. Anchovies, although not commercially important, are

of considerable importance as forage species. Many of the larger

commercially important species such as seatrout, bluefish, and mackerel

feed on them extensively.

In addition to the size of commercial landings (in pounds), the monetary

values of these fishes were examined (Table 5.4-2). With the exception

of shrimp and flounder, most of the representative important species had

a relatively low value ranging from 2.8 cents per pound (menhaden) to

18.1 cents per pound (weakfish) in 1978, the most recent year for which

full records are available. By far, the most valuable fishery; is for

penaeid shrimp, recently valued at $1.31 per pound. Consequently, the

fishery for shrimp has developed extensively. Flounders, worth 51.2

cents per pound in 1978, also have a fairly high value.

Spot are taken in large quantities, increasingly so in recent years. In

Brunswick County, anglers fish for spot during their fall movement out of

the estuary to the ocean when boaters and pier fishermen may catch in

excess of 50 pounds per person daily. In addition, trawlers and gill

netters fish commercially for this species. North Carolina landings of

spot have been high (Table 5.4-2), although the value is low (12.9 cents

per pound). Furthermore, the fishery is mostly in the central district,

with relatively small landings from the southern district. Adult

spot average 0.5 pound.

Croaker is not especially sought in the Brunswick County fisheries,

but is taken incidentally in other fishing operations. Mosc of the

commercial landings come from shrimp trawlers that pick up croaker

5-139

Table 5.4-2 Annual commercial landings (pounds) for representative important species andstatewide price per pound based on North Carolina fishery statistics.

Location

SouthernIDistrict

Central2

DistrictNorthern3

District

Statewide Price(Cents) PerPound (1978)Species Year Statewide

Spot 19781977

299,174121,246

3,771,4693,168,586

877,794515,294

4,878,4373,805,126

12.912.3

Croaker

Shrimpa.

0

19781977

19781977

19781977

19781977

121,43793,483

886,253719,527

12,04634,009

260,052252,602

12,976,37812,075,632

1,655,5113,474,815

6,776,7244,763,601

6,282,8305,881,059

6,847,6566,825,462

418,9981,405,987

4,060,5433,873,600

5,755,882,5,003,433

19,945,47118,994,577

2,960,7625,600,329

10,849,3138,671,210

12,298,76411,137,094

13.710.9

131.2129.3

18.112.1

51.244.9

Weakfish

Flounder

Mullet

Menhaden

19781977

430,917759,002

1,125,874651,098

195,442424,835

1,752,2331,834,935

192,324,170158,119,330

13.310.5

3.92.8

19781977

1Iicludes Onslow, Pender, New Hanover, and Brunswick counties.

Includes Craven, Pamlico, and Carteret counties.

3Includes Currituck, Camden, Pastquotank, Perquimans, Chowan, Bertie, Washington, Tyrell, Dare, Hyde,and Beaufort counties.

during shrimping operations. The croaker is considered a good eating

fish and is utilized by local residents. The average size of croaker

is 0.5 pound.

North Carolina has been, and continues to be, the most productive of

the southeastern states for croaker. Statewide commercial landings

in North Carolina have resulted in record catches during each of the

past five years. However, the value of croaker, 13.7 cents per pound

(Table 5.4-2), is low.

Two species of seatrout are taken in significant quantities in North

Carolina (Table 5.4-2), the spotted seatrout and the grey trout or

weakfish. Grey trout is the more common of the two species in North

Carolina and is usually caught by gill nets and angling. Statewide

landings in North Carolina reached a record catch of 10,894,313 pounds

in 1978, but the price per pound (18.1 cents) has remained low. Adult

trout average approximately 1.0 pound.

A variety of flounder species occur in North Carolina and in the Cape

Fear, but the most important species in the CFE are the southern flounder

and the summer flounder. Flounders are among the most prized food fish

taken in the estuarine waters of Brunswick County. They are caught

using trawls, gill nets, haul seines, with gigs and by angling. The

commercial market seeks flounder for restaurants and for inland buyers.

In addition, local residents consume a great deal of flounder, and

night-gigging with underwater lights is very popular in late summer and

early fall. Flounder that are taken commerciallyrange from one-half

pound to over 6 pounds apiece, with the average weight being about 1 1/2

pounds. North Carolina commercial flounder landings have been

increasing since 1970, with relatively stable catches during the past

five years. The desirability of flounder as a food fish is reflected in

the moderately high value of 51.2 cents per pound for this fish (Table

5.4-2).

The Art'la:ic me'--_en 'Arevoortii tvrannus) is not valued as a food

fish, but is heavily fished commercially for processing into fertilizer

and fish oil.

-14a1

The commercial fisheries data show high exploitation of this species

with 192 million p6unds landed in North Carolina during 1978. Landings

have exceeded 100 million pounds in each of the past five years (1974-

1978). In addition, the highest unit value occurred in 1978 (3.9 cents

per pound), although menhaden were valued at 3.8 cents per pound in -1973.

Values have fluctuated but do not seem to reflect fluctuation in catches.

Historically, the central district has been the most productive portion

of the state, but with menhaden the port of landing is determined by

the location of processing plants. Adult menhaden in the commercial

catch average 0.3 pounds.

Two species of mullet occur in the Cape Fear, although the more common

species is the striped mullet. The two species, however, are not

separated commercially. They are gill netted in the tidal creeks during

the summer and the juveniles are caught with butterfly cost nets and

used as live bait by anglers. In early fall, as mullet leave the

estuary and form large schools, haul seines are used to catch them

along the beaches.

North Carolina commercial landings of mullet have not fluctuated greatly

in recent years. Price per pound has shown a fairly steady increase in

the 1970s, increasing from 5.3 cents (1970) to 13.2 cents (1978) per

pound. Landings have been fairly evenly distributed within the districts

between years perhaps indicative of migratory features of the mullet.

The weight of adult mullet averages 0.5 pound.

The shrimping industry represents the second largest commercial fishery

in Brunswick County, with an estimated 50-75 large trawls (40-90 ft)

docking there. From May through October, the trawlers seek penaeid

shrimp in the Atlantic Ocean and account for a large portion of the

local shrimp catch. In addition to these fishermen, there are private

and small operators whose catches are not reported. The private

shrimping pressure is heavy due to fishermen from upstate and New

Hanover County who utilize the waters in Brunswick County.

5 - 14 a

The total shrimp catch (combining the three component species) forNorth Carolina statewide commercial landings (1970-1978) have variedfrom 2,960,762 to 8,440,203 pounds with the highest landings beingrecorded from the central district (Pamlico Sound and oceanic areas).The shrimp constitute one of the most valuable fishery species inNorth Carolina. Price per pound has increased each year, from 49.3cents (1970) to $1.31 per pound (1978). The average weight of anadult shrimp is .025 pounds.

* I .44s - * -

-*4; ' -. 4 :

-s k \. v . .4-

* 42&'. * .'.

- ."-,a'.

4 S b y~ I -t

A - -- 4vi- 1-'

--- -- 4 * /' -

H i-

Figxre..5.4-11 Map of the Cape rear River Escuary. Samplingstations for 1976-1978.

5-144

Table 5.4_3 Trip numbers, sampling dates and analysis periods forpostlarvae. entrained by the 3SEP, 1974-1978.

larvae and

Trip1

234567

SamplingDate

7 Lay 745 June 742 July 74

31 July 7427 Aug 74

9 Sept 7424 Sept 74

8 7 Oct9 21 Oct

10 7 Nov11 19 Nov12 4 Dec13 15 Dec14 17 Jan15 13 Feb16 23 Feb17 13 Mar18 24 Mar19 7 Apr

*20 25 Apr21 6 fay22 18 May23 4 June24 11 June25 16 June26 2 July27 16 July28 30 July29 12 Aug30 27 Aug31 9 Sept32 24 Sept

74747474747475757575757575757575757575757575757575757575757575757575767676767676767676

,6

I e

AnalysisPeriod

*

*

*

*

*

1.457

101214162024252829313435374041424446485052

14579

11121314151618192122232426272830

_2

SamplingTrip Date53 27 Apr 7654 4 May 7655 11 May 7656 25 May 7657 8 June 7658 22 June 7659 7 July 7660 20 July 7661 17 Aug 7662 14 Sept 76

.

63 5 Oct1 27 Oct2 2 Nov3 9 Nov4 16 Nov5 23 Nov6 1 Dec7 7 Dec8 13 Dec9 21 Dec

10 29 Dec11 4 Jan12 11 Jan13 18 Jan14 25 Jan15 1 Feb16 8 Feb17 L5 Feb18 22 Feb19 1 Mar20 8 Mar21 15 Mar22 22 Mar23 29 Mar24 5 Apr25 13 Apr26 19 Apr27 26 Apr28 3 May29 10 May30 17 May31 24 May32 31 May

7676767676767676767676777777777/7777777777777777777777777777777777

AnalysisPeriod

343536*38404244**465025***

8. 9101112131415161718192021222324252627282930313233343536373839404142

;34445' 6

_,

-

333435-363738394041

424344

45460

-a71484950

6 Oct22 Oct4 Nov13 Nov19 Nov24 Nov3 Dec

11 Dec16 Dec6 Jan12 Jan26 Jan3 Feb

11 Feb17 Feb3 Mar

10 Mar16 Mar30 M r -_ ,.. _;

33 7 June 7734 14 June 7735 21 June 7736 28 June 7737 6 July 7738 12 July 7739 1.9 i"uI 77-O 2' jul 7,, 7 71 7 Aug 77

5-145

Table 5.4-3 (continued)

Trip42434445464748495051525354.555657585960616263646566676869

SamplingDate

9 Aug 7716 Aug 7723 Aug 7730 Aug 77

7 Sept 7713 Sept 7720 Sept 7727 Sept 77*

40Oc 7711 Oct 7718 Oct 7725 Oct 771Nov 778 Nov 77

15 Nov 7721 Nov 7729 Nov 77

6 Dec 7713 Dec 7720 Dec 7729 Dec 77

3 Jan 7810 Jan 7817 Jan 7824 Jan 7831 Jan 78

7 Feb 7814 Feb 78

Analys isPeriod

49505152

123456789

101112131415161718192021222324

Trip707172

. 73747576777879808182838485868788899091929394959697

SamplingDa re

21 Feb 7828 Feb 78

7 Mar 7814 Mar 7821 Mar 7829 Mar 78

4 Apr 7811 Apr 7818 Apr 7825 Apr 78

2 May 7810 May 7816 May 7823 May 7830 May 78

6 June 7813 June 7820 June 7827 June 78

5 July 7811 July 7818 July 7825 July 78

3 Aug 788 Aug 78

15 Aug 7822 Aug 7829 Aug 78

AnalysisPeriod

2526272829303132333435363738

- 3940414243444546474849505152

-

* Data not included in statistical analyses.** Hydrographic data only.

*** Samples not processed.

I

5-1L6

LITERATURE CITED

1. Adams, S. M.: The ecology of eelgrass, Zostera marina (L.),

fish communities. II Functional analysis. J. Exp. Mar. Biol.

Ecol. '2, 293-311 (1976).

2. Allen, K. R.: The computation of production in fish populations.

N. Z. Sci. Rev. 8, 8 (1959).

3. American Society for Testing and Materials (ASTM). 1963.

Standard method for particle-size analysis of soils. Amer. Soc.

Test. Mat. D422-63.

4. Anderson, W. W. 1957. Early development, spawning, growth, and

occurrence of the silver mullet (Mugil curema) along the south

Atlantic coast of the United States. Fish. Bull. 119:397-414.

5. Arnoldi, D. C., W. H. Herke, and E. J. Clairain Jr. 1974.

Estimate of growth rate and length of stay in a marsh nursery of

juvenile Atlantic croaker, Micropogon undulatus sandblasted with

fluorescent pigments. In J. B. Higman (ed.), Proc. 26th Annu.

Session, Gulf Carib. Fish. Instit., New Orlears, La.

6. Barlow, J. P. 1953. Maintenance and dispersal of an endemic

zooplankton population in a tidal estuary. Ph.D. Thesis, Harvard

University, Cambridge. 166 pp.

7. Bassindale, R. 1936. The developmental stages of three English

barnacles Balanus balanoides (Linn.), Chthamalus stellatus

(Poli), and Verruca stroemia (Muller). Proc. Zool. Soc. Lond.,

Part I:57-74.

8. Bearden, C. M. 1964. Distribution and abundance of Atlantic

croaker, Micropogon undulatus, in South Carolina. Contrib. Bears

Bluff Lab. 40, 23 p.

9. Bigelow, H. G. and W. C. Schroeder.: Fishes of the Gulf of Maine.

Fish. Bull., U. S. Fish and Wildl. Serv. 53, 1-577 (1953).

10. Boesch, D. F.: A new look at the zonation of benthos along the

estuarine gradient. In: Ecology of marine benthos, pp. 245-266.

Ed. by B. C. Coull. Columbia: University of South Carolina Press

(1977).

11. Bousfield, E. L. 1955. Ecological control of the occurrence of

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