Black Sea Bass – Northern Stock

Coastal-Pelagic/ASMFC Working Group Review

June 15, 2010

Update of assessment approach adopted by the Data Poor Stocks Working Group ( Dec 2008) and the 2009 assessment (June 2009).

Approach:

Length-based model of population parameters

- require time series of catch, survey indices

Compare results to biological reference points to determine stock status

Produce projections based on model results

Life History –

Distributed Maine through Gulf of Mexico

Managed as single stock north of Cape Hatteras

Protogynous hermaphrodite: Transition to male at age 2-5

Seasonal migrations inshore/offshore

Maximum age 15 (?)

50% mature 21 cm

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

Length (cm)

Pro

port

ion

Mat

ure

Black sea bass size at maturity from NEFSC spring surveys

Black Sea Bass size limits

8

9

10

11

12

13

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007Year

Min

imu

m s

ize

(in

ches

)

Commercial

Recreational

Commerical Landings

0

2

4

6

8

10

1219

39

1942

1945

1948

1951

1954

1957

1960

1963

1966

1969

1972

1975

1978

1981

1984

1987

1990

1993

1996

1999

2002

2005

2008

Year

MT

(000

s)

28.8%

17.2%37.6%

8.3%

0.2%

8.0%

29.8%

21.5%

31.9%

7.8%0.3%

8.7%

large

jumbo

medium

small

ex small

unclassified

2008 and 2009 commercial black sea bass landings

Values in blue - estimates from commercial ratio

Recreational Landings

0

1

2

3

4

5

6

Year

MT

(000

s)

Recreational Discard weight

Discard weight estimated using landing mean weight

Recreational Discards

0

100

200

300

400

500

600

700

800

900

Year

MT

(00s

)

OT from observer 1989-2008

Pot and handline from VTR 1994-2008

2009 estimate from series average

Commercial Discards

0

50

100

150

200

250

300

350

400

450

500

Year

MT

Black sea bass catch estimates

Rec discard mortality = 25% Com discard mortality = 25-50%

0

1

2

3

4

5

6

7

8

9

Year

MT

(000

s)

com disc

rec disc

rec landed

com landed

43%

39%

14%

4%

Commercial landings

recreational landing

rec discard losses

com discard losses

2005-2009 average sea bass catch components

1990

0

100

200

300

400

500

600

700

800

900

1000

Length (cm)

Fre

quen

cy (

000s

)1985

0

100

200

300

400

500

600

700

800

9001 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

qu

ency

(00

0s)

1995

0

100

200

300

400

500

600

700

800

900

1000

Length (cm)

Freq

uenc

y (0

00s)

2000

0

100

200

300

400

500

600

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

quen

cy (0

00s)

Combined Recreational/Commercial landings length frequency

1985

1990

1995

2000

2001

0

100

200

300

400

500

600

700

Length (cm)

Freq

uenc

y (0

00s)

2002

0

100

200

300

400

500

600

700

800

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

quen

cy (0

00s)

2003

0

100

200

300

400

500

600

700

1 4 7 10

13

16

19

22

25

28

31

34

37

40

43

46

49

52

55

58

61

64

Length (cm)

Fre

qu

ency

(0

00

s)

2004

0

50

100

150

200

250

300

350

400

450

500

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

qu

ency

(00

0s)

Combined Recreational/Commercial landings length frequency

2001

2002

2003

2004

2005

0

50

100

150

200

250

300

350

4001 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

quen

cy (

000s

)

2006

0

50

100

150

200

250

300

350

400

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Fre

quen

cy (0

00s)

2007

0

50

100

150

200

250

300

350

400

450

500

Length (cm)

Freq

uenc

y (0

00s)

Combined Recreational/Commercial landings length frequency

2005

2006

2007

2008

0

50

100

150

200

250

300

350

400

Length (cm)

Freq

uenc

y (0

00s)

2008

2009

0

50000

100000

150000

200000

250000

300000

3500001 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64

Length (cm)

Freq

uenc

y

20.0

22.0

24.0

26.0

28.0

30.0

32.0

34.0

36.0

Year

Leng

th (c

m)

Mean and Median length of sea bass landings

median

mean

Northeast Fisheries Science Center Trawl Survey

Spring offshore strata 1968 – 2009 (Bigelow conversion coefficient = 3.416)

Winter offshore strata 1992 – 2007

Loge transform indices

NEFSC Indices of sea bass adult abundance (>22 cm)

(stratified mean #/tow)

1.0

2.0

3.0

4.0

5.0

6.0

7.0

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Mea

n #

/tow

spring offshore

winter offshore

NEFSC Spring and Winter indices of juvenile abundance (stratified mean #/tow)

0.000.100.200.300.400.500.600.700.800.901.00

Year

Mea

n #/

tow

-spr

ing

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Mea

n #/

tow

-win

ter

SCALE model

SCALE model (P. Nitschke NMFS,NEFSC)

Length based catch at age model

Inputs : NEFSC spring (1968-2009) and winter surveys (1992-2007)

adult (> 22 cm) and recruitment (< 14 cm)

Survey length frequencies (1968-2009,1992-2007)

Fishery catch series (1968-2009)

Fishery length frequencies (1984-2009)

Selectivity periods (1984-1997, 1998-2000, 2001-2009)

Mean length at age and std. deviations

Length-weight equation (from survey series)

Natural mortality estimate (0.4)

Sea Bass growth used in SCALE

Mean length + 2 stdev

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12

Age

Leng

th (c

m)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Length (cm)

Sele

ctiv

ity

1968-1997

1998-2000

2001-2008

Selectivity used in the SCALE model

Model results influenced by presence of juvenile indices, weighting factors, etc.

Which is correct model?

Adopted model averaging approach (Burnham and Anderson (2002)

Scale modeling approach:

Run Number 1 2 3 4 7 8 9 10 11 12

Total Objective Function 266.6 261.4 297.3 291.7 269.0 256.1 257.1 252.5 263.3 266.6

Weight on Catch Weight 15 15 15 15 20 20 25 25 25 25

Weight on Recruitment Index 1: spring 15 15 15 15 15 15 15 15 15 20

Winter 2007 juvenile index x x x x x x x

Weight on Recruitment Index 2: winter 15 15 15 15 15 15 15 15 10 10

Autumn juvenile index series included x x

Weight on Recruitment Index 3: fall 15 15

Weight for Adult Index 1: spring ln 15 15 15 15 15 10 10 10 15 15

Weight for Adult Index 2: winter ln 15 15 15 15 15 10 10 10 15 15

Observed and estimated average (+ 2 std dev) black sea bass catch

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Cat

ch (

mt)

NMFS Spring index – predicted vs observed (index +1)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.819

68

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Mea

n #

/tow

predicted

observed

NMFS Winter index – predicted vs observed (index +1)

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Mea

n #

/tow predicted

observed

Wt’d Average Fishing mortality + 2 std dev from SCALE model estimates

Fmsy

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Fis

hin

g M

orta

lity

Wt’d Average Recruitment + 2 std dev from SCALE model estimates

Recruitment (age 1)

0

10000

20000

30000

40000

50000

60000

70000

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Abu

nda

nce

(000

s)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Bio

mas

s (m

t)Wt’d Average Total Biomass + 2 std dev from SCALE model estimates

Bmsy

Wt’d Average Total Abundance + 2 std dev from SCALE model estimates

-

20,000

40,000

60,000

80,000

100,000

120,000

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

Ab

un

dan

ce (

000s

)

Wt’d Average Spawning Stock Biomass + 95% CI from SCALE model estimates

-

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

year

SS

B (

mt)

SSBmsy

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0

SSB (000s mt)

Fis

hing

Mor

talit

y

SSBmsy/2 = 6,269 mt

Fmsy = F40%= 0.42

SSBmsy =12,537 mt

2009

Relationship between SSB and F

Projection approach

Use predicted output as new input. Input F for projections and allow model to predict catch.

Survey data in 2009 and 2010 treated as missing.

2010 Catch assumed equal to quota plus average discard.

2010-2012 lf 5 year average

Average spring and winter indices

Average recruitment variation, starting recruitment and starting F

Ref pts

MSY 3,903

SSBmsy 12,537

Bmsy 13,977

Fmsy 0.42

Projection if F2010 = F2008

F Landings (mt) Discards (mt) SSB (mt)

F2011=Fmsy 0.42 2,772 693 13,872

F2011 = 75% Fmsy 0.32 2,166 542 14,636

F2011=F2009 0.29 1,974 493 14,677

Quota=status quo 0.23 1,633 408 15,335 (catch = 4.5 million lbs)

Retrospective patterns in typical model run

run 7 Fishing mortality

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

F

run 7 Recruitment

0

10

20

30

40

50

60

70

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

recr

uit

s (m

illi

ons)

run 7 Total Biomass

0

5

10

15

20

25

1968

1971

1974

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

bio

mas

s (0

00s

mt)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Year

Fish

ing

Mor

talit

y

DPWG

2009

2010

0

2000

4000

6000

8000

10000

12000

14000

Year

SSB

(m

t)

DPWG

2009

2010

Comparison to previous

assessments

NEFSC Spring offshore survey-2004

1st Quartile (Lowest) 2nd Quartile 3rd Quartile

4th Quartile (Highest) 100 Fathom Depth

35.00

36.00

37.00

38.00

39.00

40.00

41.00

42.00

43.00

Latit

ude

-76.00 -75.00 -74.00 -73.00 -72.00 -71.00 -70.00 -69.00 -68.00Longitude

Catch NumbersBLACK SEA BASS

Spring 2005

NEFSC Spring offshore survey-2005

NEFSC Spring offshore survey-2006

NEFSC Spring offshore survey-2007

NEFSC Spring offshore survey-2008

NEFSC Spring offshore survey - 2009