AST/IBIS – Stocking Workshop

Case Study - River Bush, Northern Ireland.

R. Kennedy1, W. Crozier1, D. Ensing1, J. Kane2, P. Prodohl3 & C. Johnston3.

1) ABFI, 2) Dept Culture, Arts & Leisure, 3) Queens University Belfast.

Contents

• The River Bush as a monitored river.• Pressures on the River Bush salmon stock.• Enhancement on the River Bush, history, rationale

& management objectives.• Review of enhancement activities.

40 0 40 Miles

N

EW

S

Main Salmon Producing Rivers In N. IrelandRiver Bush

Bush RiverLength 67 kmCatchment Area 340km2

5 km

River Bush Salmon Station

River Bush Salmon Station• Facility established in 1973-4.

• A series of upstream/downstream traps were set up at the station (Adult/Smolt).

• A series of long term databases on salmon survival established.

• One of relatively few long term monitoring stations across the Atlantic basin.

SMOLT TRAP

ADULT TRAP

Extensive Annual

Electrofishing

OVA

ALEVIN

PARR

SMOLT

POST SMOLT

ADULT

The complete Atlantic Salmon Lifecycle is monitored on the River Bush stock.

Pressures and Challenges to Salmon Production on the River Bush

Pressures on Freshwater Production – Habitat Issues

• Arterial Drainage Scheme.• Excessive weed growth; degradation of

spawning habitats.• Intensive agricultural practices.• Degradation of the riparian zone.• Reduction in habitat quality 1980s-1990s.

ARTERIAL DRAINAGE

EXCESSIVE WEED GROWTH

Pressures on Freshwater Production - Predation

• Major issues with avian predation.• Kennedy & Greer (1988)

estimated total daily predation by cormorants on the River Bush to range c. 653-1214 smolts in late April/early May.

• Potential annual predation rates c. 51-66% of the total smolt run.

No. of breeding pairs of cormorants on Sheep Island (Kennedy & Greer, 1988)

The Impact of these Pressures on the River Bush

Salmon Stock.....

River Bush Smolt Run 1973-1996

1983 0+ Salmon Survey

SQ Category

SQ Category

1996 0+ Salmon Survey

R. Bush Wild Ova Deposition & Compliance with Conservation Limit

CL

Enhancement Plan

• Enhancement stock using hatchery produced 0+ age class salmon.

• Target barren/underproductive freshwater habitats which historically supported juvenile fish.

• Improve freshwater production and compensate for loss/deterioration of spawning areas.

• Increase annual smolt production from the river to a target of 20,000 fish.

• Assist the stock to consistently attain CL.

• Monitor impact and outcomes of the management action.

Management Objectives

R. Bush Stocking Plan Challenge

Overstocking/competitive interaction with wild juveniles.

Relatively low survival of introduced juvenile life stages

Removal of wild spawners ‘broodstock mining’

Effective monitoring of outcomes.

MitigationReference to extensive annual electric

fishing survey, i.d. ‘recruitment gaps’

Implementation of best practice during stocking (low density/acclimation etc.)

Utilisation of ranched salmon, derived from wild stock and outcrossed annually

Long term monitoring capacity; EF, smolt trap etc.

Stocking History

• Between 1997-2007 c. 3.87 million 0+ salmon stocked directly into freshwater habitats in the R. Bush.

• Between 1997-2001 unfed fry stocked, 2002 onwards unfed fry plus fed summerling fry stocked.

Estimation of Survival –Wild Cohorts

Ova CohortYEAR X

Total smolt production

Ova to smolt survival

YEAR

TOTALOVA(M

)

TOTALSMOLT

S 1+ 2+ 3+

TOTALSMOLT

S

OVA-SMOLT

%

year x x+2 x+3 x+41974 1.84 15717 4003 11714 0 15717 0.851975 1.94 19641 9307 10318 16 19641 1.011976 1.59 22378 9375 12910 93 22378 1.401977 1.73 36360 14194 21802 364 36360 2.101978 1.22 22243 2931 19284 28 22243 1.821979 1.07 12412 855 11472 85 12412 1.161980 1.16 12440 3037 9239 164 12440 1.071981 1.45 13913 1455 12458 0 13913 0.951982 1.58 33623 14346 18535 742 33623 2.121983 2.18 28104 11474 16401 229 28104 1.291984 1.72 30790 13371 17350 69 30790 1.791985 1.17 21910 1487 20035 388 21910 1.871986 3.03 21216 2052 18888 276 21216 0.701987 4.79 19008 3718 15218 72 19008 0.391988 3.43 13893 2318 11556 19 13893 0.411989 4.6 20963 5726 15233 4 20963 0.461990 1.06 8610 3219 5281 110 8610 0.811991 2.44 13548 4736 8812 0 13548 0.561992 2.97 15742 2661 13074 7 15742 0.541993 2.57 4135 1071 3064 0 4135 0.161994 3.0 10495 2647 7746 102 10495 0.351995 2.25 19560 4703 14728 129 19560 0.87

Estimation of Contribution – Supplemented Wild Cohorts

1994

1991

1990

1989

1988

1987

1986

19851984

1983

1982

1981

1980

19791978

1977

1976

1975

1974

1973

1993

1995

2006

2005

2004

2003

2002

2001

2000

1999

1998

19971996

1992

1.0

35000

30000

25000

20000

15000

10000

5000

1.5 2.0 4.54.03.53.02.5

Sm

olts

Ova

Fitted 1973-1995

Variability in Survival Stock Recruitment Relationship

Model and Predict Smolt Production from Wild Ova Cohorts

Smolt output from annual ova cohorts

From: Kennedy, R.J., Crozier, W.W., Allen, M.M (2012). Journal of Fish Biology, 81(5):1730-1746.

Ground Truthing Survival Estimates.

Use of genetic tools for the monitoring of the River Bush supplemental stocking programme – Unfed Fry

• 40 unique family pairings 40 male + 40 female broodstock (2002).

• Fertilized eggs (avg 3,798 per family) maintained in the hatchery.

• 90,500 unfed fry were stocked in the upper reaches of the R Bush (Characterized by limited suitable spawning habitat).

• During the smolt runs of 2004 and 2005, 1,212 and 1,262 (total N = 2,474) smolts trapped & sampled for genetic analysis.

• Broodstock screened for 25 microsatellite markers – following modelling work (FAP and COLONY software), all smolts screened for a selected informative marker panel consisting of 6 markers (100% assignment to family).

• .

Summary results - parentage assignment

Cohort TSR Capt %No. Matches

to Broodstock

Estimated No. Hatchery-reared

smolts in TSR

% of surviving Hatchery-reared

smolts released in TSR

2,004 23,389 1,212 5.18 5 110 0.12

2,005 22,792 1,262 5.54 21 501 0.55

Total 46,181 2,474 5.36 26 595 0.66

TSR – Total Smolt RunCapt – smolts intercepted and sampled at the River Bush Research Station

Bush RiverFed fry survival experiment 2007

5 km

River Bush Salmon Station

30,165 Fin clipped summerlings stocked in 2008 Aug/Sep

Survival of Fed 0+ Summerlings

• 2008 an experimental group of 30,165 summerlings adipose fin clipped and stocked.

• Areas selected after electric fishing surveys to reduce overstocking/competition.

• 1+ & 2+ FC smolts picked up in 2009 & 2010.

• Total survival fry to smolt = 5.12%

Management Outcomes

• Smolt runs

• Adult escapement/Attainment of CL.

Freshwater Production – Smolts

Monitoring Phase

Management Phase

Recent Attainment of CL

Biological Characteristics – Smolts

Younger 1+ stocked origin smolts

Smaller

Lower CF

Biological Characteristics – Smolts

Stocked origin smolts

Differential Run Timing

Younger

Potential Implications for Marine Survival

• Older larger smolts; higher survival.

• Risk from enhancing younger smolts?

Potential Implications for Marine Survival

From: Russell et al (2012). ICES J. Mar. Sci. 69 (9): 1549-1562 .

Critical local importance of smolt run timing on the R. Bush.

Appraisal of Objectives

• Increase annual smolt production from the river to a target of 20,000 fish.

• Assist the stock to consistently attain CL.

• Monitor impact and outcomes of the management action.

Changing Management Priorities?

Scientific assessment conducted on the Bush has been useful to local management e.g. Abundance is not all important.

Stocking was a relatively ‘quick’ option BUT it cannot address and solve underlying habitat issues.

Stocking has RISKS....

Important to maximise the production of wild spawned smolts with optimum fitness.

Other ‘longer term’ conservation tools include habitat & fishery management

Fishery Management to Maximise Wild Escapement to NI Rivers.

Cessation of mixed stock fisheries

Catch & Release Angling

Habitat Improvement and Restoration on the River Bush

Gravel Addition Weed Clearance

+ +

Future, the next phase....

Emphasis on maximising wild production via habitat management.

Collaborative assessment of overall lifetime fitness of stocked fish.