Linkages between climate, growth, competition at sea, and production of sockeye salmon populations in Bristol Bay,

Alaska, 1955-2000

J. Nielsen (USGS) & G. Ruggerone (NRC)

North Pacific Ocean – a Highly Productive Ecosystem2002 U.S. North Pacific exvessel harvest value = $1.13 billion

Pacific Rim Salmon Runs, 1951-2001

0

200

400

600

800

Salm

on

ru

n (

million

s)

50 60 70 80 90 100

Year

Coho

ChinookChum

SockeyePink

Climate Change and North Pacific Salmonid Species Abundance Shifts

-4

-3

-2

-1

0

1

2

3

PD

O I

nd

ex

51 56 61 66 71 76 81 86 91 96 01

Year

1997/98El Nino

1976/77Oceanregimeshift

Regime Shift Impacts on Marine PopulationsCompiled by D. L. Alverson (NRC)

Eastern North Pacific Winter Sea Surface Temperature

-3

-2

-1

0

1

2

No

rmali

zed

SS

T(

Z)

65 70 75 80 85 90 95 00

Year

Oceanregimeshift

Bristol Bay Sockeye Salmon Run, 1951-2002

0

20

40

60

80

So

ckeye r

un

(m

illi

on

s)

51 56 61 66 71 76 81 86 91 96 01

Year

1997/98El Nino

1976/77Oceanregimeshift

Key Question

What biological and physical climatic feedback mechanisms have influenced

historic and current abundance patterns in Bristol Bay sockeye salmon?

New Use for an Old Tool: Salmon Scales

Focus

FW1

FW2

FWPL

SW1

SW2

SWPL

Salmon Size Related to Scale Radius

100

200

300

400

500

600

Scale

rad

ius (

µ)

30 40 50 60 70 80 90 100 110

Sockeye length (mm)

r2 = 0.96

Davis et al. 1990; Zimmerman 1991

Sockeye salmon growth using salmon scale annuli & circuli measurements

Ocean Carrying Capacity Hypotheses Greater salmon abundance is related to greater early marine growth

in coastal waters.

Greater salmon abundance is associated with reduced growth during older life stages (density-dependence).

Competition during freshwater & marine life-stages can reduce growth and survival.

Highly migratory salmon may compete with conspecifics

originating from distant natal rivers.

Peterman 1984; Ishida et al 1993; Rogers & Ruggerone 1993; Welch & Parsons 1993; McKinnell 1995; Pyper & Peterman 1999; Pearcy et al. 1999

Kvichak Sockeye Growth During First Two Years at Sea

-2

-1

0

1

2

Norm

alize

d g

row

th (

Z)

52 57 62 67 72 77 82 87 92 97

Year at sea

Climate shift

Salmon Abundance Linked to Early Ocean Growth, 1955-2000

0

20

40

60

80

Weste

rn A

K s

ockeye (

million

s)

1.4 1.5 1.6 1.7 1.8 1.9

Kvichak SW1&2 scale growth (mm)

Kvichak Sockeye Growth During Third Year at Sea:Density-dependent

-2

-1

0

1

2

3

Norm

alize

d g

row

th (

Z)

52 56 60 64 68 72 76 80 84 88 92 96

Year at sea

Climate shift

• Asian pink salmon are highly abundant during odd numbered years.

• Bristol Bay sockeye salmon overlap with Asian pink salmon during their 2nd and 3rd years at sea.

• Pink and sockeye salmon have similar diets on high seas.

• Food consumption of both species declines in odd yrs.

• Sockeye diet changes more than pink diet in odd-yrs.

• Few wild or hatchery pink salmon originate from Bristol Bay.

Facts Supporting Competition Hypothesis

Eastern Kamchatka Pink Salmon Runs, 1957-2002

0

25

50

75

100

Ru

n (

million

s)

57 61 65 69 73 77 81 85 89 93 97 01

Year

Hatchery Pink Salmon Release

0

500

1000

1500

Pin

k sa

lmon r

ele

ase

(m

illio

ns)

50 60 70 80 90

Release year

Overlap of Asian pink & Bristol Bay Sockeye salmon

Sockeye growth reduced during odd years at sea (2nd & 3rd yrs)

-3

-2

-1

0

1

2

3

Norm

alize

d g

row

th (

Z)

53 57 61 65 69 73 77 81 85 89 93 97

Year at sea

Even-numbered year

Odd-numbered year3rd year at seamean = 612 ± 54 µ

Asian Pink Salmon Affect Adult Sockeye Length, 1958-2000

540

550

560

570S

ock

eye l

en

gth

(m

m)

0 20 40 60 80

Bristol Bay sockeye run (millions)

1977-2000

1958-1976

540

550

560

570

So

ckeye l

en

gth

(m

m)

0 50 100 150 200 250 300 350

Asian Pink salmon run (millions)

Smolt to Adult Survival, 1977-1997

-45% -26%

0

5

10

15

20

25S

urv

ival at

sea (

%)

Age 1. Age 2.

Freshwater age

Odd 2ndyr

Even 2ndyr

Even 2nd yr

Odd 2ndyr

59 Million Fewer Sockeye, 1977-1997(>$310 million)

0

3

6

9

12

Ad

ult

sockeye s

alm

on

(m

illion

s)

Egegik Naknek Ugashik Nushagak

Sockeye stock

Even 2nd yr

Odd 2nd yr

Implications of Feedback between Global Change & Competition Effect on Salmon Survival

• Climate feedback processes can impact salmon production on multiple scales.

• Climate change influence on local production of salmon may have unintended impacts on distant stocks.

• Natural and anthropogenic fluctuations in salmon production and shifts in food web dynamics may impact ESA protected salmon species throughout the North Pacific Ocean.

• These findings provide evidence of the need for “salmonid ecosystem management” looking at both freshwater and marine feedback patterns in salmon.

Acknowledgements: E. Farley, P. Hagen, B. Agler,J. Meka, D. Rogers, K. Myers, S. Ignell, M. Zimmerman