The influence of variable marine survival on fishery management

objectives for wild steelhead

Dan Rawding & Charlie Cochran

Population Monitoring Program

• Adult and smolt population estimated using mark-recapture or mark-resight

• Trout Creek adult census or trap count 1993-05 except 1995,96,& 97 -timing & redd surveys

• Precision of mark-recapture population estimates (95%CI) > + 20%

• Wild Spawner equivalents– Reproductive success of hatchery steelhead to the

smolt stage ~ 30% (Kostow 2003)– Reproductive success of hatchery steelhead to the

adult stage ~ 12% (Leider et al. 1990 & Hulett et al. 1996)

Wind River SteelheadBiological Information

• ~95% summer and ~5% winter steelhead• Segregation of race is due to Shipherd Falls

– 4 falls/cascades from 2 to 4 meters

• Summer steelhead sex ratio ~2:1 (F:M)• Repeat spawner rate ~ 6%• Repeats both spawners & recruits• Spawner-Recruit modeling assumes steelhead

are semelparous– therefore Smolt to Adult Survival (SAS) includes

repeats

Out of Subbasin Information

• Unaccounted for loss between BON and Shipherd Falls is ~17% and assumed to be harvest from Zone 6 and sport fishing

• Mortality not accounted for– BON Adults 1.4% & Smolts 13.4%– Caspian Terns (Rice & Sand Islands)~10%– Cormorants ~2%– Marine Mammals Predation (2%)– Mainstem fishing below BON (2%?)– Northern Pikeminnow predation ?

Terms

• Spawner-Recuit (SR) or Spawner-Recuit-Relationship (SRR)

• SRR– Assume lognormal errors– Beverton-Holt (BH)– Ricker (R) – Hockeystick (HS)– Quadratic & Logistical Hockeystick(QHS,LHS)

SRR Reference PointsBeverton Holt

0

400

800

1200

1600

2000

0 400 800 1200 1600 2000

Spawners

Re

cru

its

BH

Rplc

1/2 K

Hockeystick

0

400

800

1200

1600

2000

0 400 800 1200 1600 2000

Spawners

Re

cru

its

HS

Rplc

S* or MSY

Ricker

0

400

800

1200

1600

2000

0 400 800 1200 1600 2000

Spawners

Re

cru

its

R

Rplc

MSP

Logistical Hockeystick

0

400

800

1200

1600

2000

0 400 800 1200 1600 2000

Spawners

Re

cru

its

LHS

Rplc

NEQ KProd

Wind River Steelhead, Spawn Years 1993-2002

0

200

400

600

800

1000

0 200 400 600 800 1000

Spawners

Rec

ruit

s

Obs

Wind River Steelhead, Spawn Years 1993-2002

0

200

400

600

800

1000

0 200 400 600 800 1000

Spawners

Rec

ruit

s

Obs

BH

R

HS

QHS

LHS

Fishery Management

• Is there a relationship between spawners & recruits?

• Would more data help?

• What is wrong?

Parameter BH R HS QHS LHSIntrinsic Productivity NA 5.0 2.4 3.3 30.7Capacity/ Inflection 480 339 200 145 NA

Wind River Steelhead

0%

2%

4%

6%

8%

10%

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Smolt Outmigration Year

Sm

olt

to

Ad

ult

Su

rviv

al

• No, No, It’s the ocean• Smolt to adult survival ranged from 1% to 10%, or by a factor of 10

Wind River Steelhead, Spawn Year 1993-2004

0

10000

20000

30000

40000

50000

0 500 1000 1500

Wild Equivalent Spawners

Sm

olt

s

Obs

BH

R

HS

QHS

LHS

Trout Creek, Spawn Year 1992-2003

0

1000

2000

3000

4000

5000

0 20 40 60 80 100

Wild Equivalent Spawners

Sm

olt

s

Obs

R

HS

QHS

LHS

BH

Wind River Steelhead, Spawn Year 1993-2002

0

400

800

1200

1600

0 400 800 1200 1600

Wild Equivalent Spawners (R=f(S) * avg MS)

Re

cru

its Obs

BH

RHS

QHSLHS

Rplc

Wind River Steelhead, Spawn Year 1993-2002

0

400

800

1200

1600

0 400 800 1200 1600

Wild Equivalent Spawners (R=f(S) * low MS)

Rec

ruits

ObsBH

RHS

QHSLHS

Rplc

Wind River Steelhead, Spawn Year 1993-2002

0

400

800

1200

1600

2000

2400

0 400 800 1200 1600

Wild Equivalent Spawners (R=f(S) * high MS)

Rec

ruits

ObsBH

RHS

QHSLHS

Rplc

Wind River Steelhead, Spawn Years 1993-2002

0

400

800

1200

1600

0 400 800 1200 1600

Spawners

Rec

ruit

s Obs

BH

R

HS

QHS

LHS

Possible Solutions

• Annual recruitment adjustment based on marine survival index (climate, hatchery steelhead survival, wild steelhead survival)

• Covariate (climate, hatchery or wild steelhead survival) into SRR – Two Stage SRR

R = aS/(1+ aS/B) * MS- Hatchery smolt survival

R = aS/(1+ aS/B) * (HS)c

Possible Solutions (continued)

• PDO or other ocean/climate index• PDO adjusted for smolt outmigration year

Wind River Steelhead

0%

2%

4%

6%

8%

10%

-1.5-1.0-0.50.00.51.01.5

PDO

Sm

olt

to

Ad

ult

su

rviv

al

Fishery Management Objectives

• Maximize Harvest?– Maximum Sustainable Yield (MSY)– MSY as lower bound

• Maximize fishing opportunity (C&R)?• Maximize/maintain Freshwater Production?

– S* = minimum escapement to maximize smolt yield– ½ K = freshwater production @ 50% of capacity

• Maintain Genetic Diversity?– 500 spawners– WSP - 3000/ average age @ maturity (600 spawners)

Wind River MSY objectives

SAS prod Inflection S-msy prod cap S-msy prod Inflection S-msy1% 0.59 0.70 0.52% 1.19 1406 117 1.39 1013 131 1.03% 1.78 1406 372 2.09 1520 324 1.5 533 5334% 2.37 1406 534 2.78 2026 487 1.9 533 5335% 2.96 1406 648 3.48 2533 630 2.4 533 5336% 3.56 1406 734 4.18 3039 759 2.9 533 5337% 4.15 1406 801 4.87 3546 879 3.4 533 5338% 4.74 1406 856 5.57 4052 990 3.9 533 5339% 5.33 1406 901 6.26 4559 1094 4.4 533 533

10% 5.93 1406 940 6.96 5065 1192 4.8 533 533

Ricker Beverton-Holt Hockeystick

Summary

• MSY goals for low (3%)ocean survival 324 - 533• MSY goals for hi (6%) ocean survival 533 - 759• MSY goals for avg(4.5%)ocean survival 533-595• MSY goals are highly variable depending on

SAS - 117 (1%) to 1192(10%)• Precautionary approach suggest MSY as lower

bound• MSY goals for small steelhead populations may

compromise genetic diversity

Summary

• Current Wind River escapement goal 1,000 to 1,300 based on habitat model with good marine survival

• MSY goals for 4.5% SAS 533 - 595• Minimum genetic goal 500 - 600 spawners• SRR goals freshwater productivity (517 –

729)– Beverton-Holt Hockeystick

• ½ K = 729 S* = 532, S* for QHS = 517

Fishery Management

• Wind River Steelhead are listed under ESA• Currently, WDFW manages steelhead

commercial & recreational fishery impacts in the Wind River and other Lower Columbia River populations for less than 10%

• Fishery management and escapement objectives for Wind River will be a compromise of science and policy

• Recovery planners advocate “extra spawners” (above MSY) to take advantage of habitat restoration or lessen extinction risk

Fishery Management

• When fisheries are managed for fixed escapement goals, they are more likely to meet escapement objectives

• When fisheries are managed for fixed harvest rates, they are more likely to meet fishing objectives

• If we desire more precise management, a fishery management with multiple thresholds or controls between 300 and 800 adults could be developed for this population (BC approach with conservation and target reference points)