Survival at Sea A. Average Marine Mortality B. Life Cycles of specific populations C. Size-Survival D. Variation among years E. Ocean – Upwelling F. Long-term Trends G. Predators

Species Average survival rate

chum 1.4%

pink 2.8%

Chinook 3.1%

coho 10.4

sockeye 13.1%

Average percent marine survival for wild populations

In any population, there is considerable variation in marine survival

0

5

10

15

20

25

1949

1952

1955

1958

1961

1964

1967

1970

1973

1976

1979

Chi

lko

smol

t - a

dult

surv

ival Wild Chilko Lake sockeye salmon

Stage-specific mortality and the dynamics of Fraser River chum salmon

Adults 387,210 Females 200,444 Eggs per female 3,250 Fry 91,990,000 Egg to fry survival 14.17% Adults 812,893 Fry to adult survival 1.19% Return per spawner 2.16

Beacham and Starr. 1982. Fishery Bulletin 80: 813-825

Stage-specific mortality of wild Lewis River chinook

Eggs per female 5,122 Egg to fry survival 65.3% Fry per female 3,345 Fry to smolt survival 10.05% Smolts per female 336 Smolt to adult survival 2.38 Adults per female 8 Escapement 48.8% Returning spawners per female 3.9

McIsaac, D.O. PhD thesis. University of Washington

Stage-specific mortality of Bella Coola pink salmon

Life history stage Mortality Survivors Fry * 60,000,000 1st 40 days 65% 21,000,000 final 410 days 85% 3,150,000 Fishing * 85% 472,500 50% females * 236,250 2,000 eggs/female * 472,500,000 Egg to fry * 87.3% 60,000,000

R.R. Parker. 1968. J.F.R.B.C. 25: 757-794

* Hypothetical values assumed to balance the cycle

Mortality should be is highest on small salmon, soon after they enter the ocean. As they grow, mortality rates are assumed to

decrease (e.g., Karluk Lake sockeye salmon: Ricker 1976).

0200400600800

10001200140016001800

1 5 9 13 17 21 25

Months at sea

Wei

ght (

g)

0

10

20

30

40

50

60

Num

ber o

f sal

monweightnumber

0123456789

0 20 40 60 80 100

MarchApril

Number of days at large

% m

orta

lity

per d

ay

Estimates of average daily mortality of unfed chum salmon fry from Southeast Alaska

(Wertheimer and Thrower 2007 AFS Symposium 57)

8.1%

1.6% 2.3%

4.1%

5.9%

3.9%

Estimated mortality rate of Columbia River and coastal Oregon coho salmon (1982-1985)

Date Days at sea Millions of salmon

% mortality per day

% mortality per period

May 1 0 35.24

June 17 47 8.50 2.92 75.9

Sep 11 133 3.87 0.91 54.5

Sep 1 488 1.11 0.35 71.3

William Pearcy and Joseph Fisher, Oregon State University

What controls the survival of salmon at sea?

• Attributes of the fish – species – size – entry point – wild vs. hatchery reared – migration date

• Attributes of the environment • Predators

0

5

10

15

20

25

0 50 100 150 200 250

Smolt length (mm)

% m

arin

e su

rviv

al

pink

chum

sockeye

chinook

coho

cutthroat

steelhead

Smolt size and variation in marine survival among species

Geographic variation in marine survival of wild coho salmon

Region Site Years SurvivalSE Alaska Auke Cr. 1980 - 2004 20.3

Berners R. 1990 - 2004 17.8Hugh Smith L. 1984 - 2004 12.9Taku R. 1992 - 2004 12.0

N British Columbia Lachmach R. 1988 - 2003 10.0Zolzap Cr. 1993 - 2004 5.9

S British Columbia Black Cr. 1986 - 2004 7.1Salmon R. 1987 - 2004 8.5

Puget Sound Big Beef Cr. 1979 - 2003 17.2Deschutes R. 1980 - 2004 13.1

WA coast Queets R. 1982 - 2003 5.5Bingham Cr. 1983 - 2004 4.4

Shaul et al. 2007 NPAFC Bull. 4: 93-104

Smolt size South (< 55 N)

Middle (56–60 N)

North (> 60 N)

Small (71-76 mm) 5.9 16.7 17.7

Medium (97 mm) 12.6 25.1 32.0

Large (134-139 mm) 17.1 37.0 39.1

Interaction between smolt size and latitude on survival of sockeye salmon: Bigger is

better, and northerly populations do better

(Koenings et al. 1993)

Salmon smolts vary in size among years.

Does size affect their likelihood of survival?

Henderson and Cass. 1991. CJFAS.

Example:

Chilko Lake sockeye salmon:

length distributions among years

Mean smolt fork length was not related to marine survival variation among years

Mean length (mm)

Surv

ival

(%)

72 82 92 102

0

1

0

20

30 Chilko Lake

sockeye salmon

Salmon smolts vary in size within years.

Does size affect their likelihood of survival?

Henderson and Cass. 1991. CJFAS.

Chilko Lake sockeye salmon

Growth History

Scale Radius

Fish

Len

gth Individual circuli

Relationship between fish length and scale radius

0 1 2 3 4 5

100 90 80 70 60 50 40 30 20 10 0

Scale Radius (mm)

Fork

Len

gth

(cm

)

Ishida and Mathews 1989.

Within a year, larger Chilko Lake sockeye salmon smolts were more likely to survive than smaller ones

Surv

ival

(%)

70 80 90 100

0

5

10

1

5

20

Length (mm)

Year 1 Year 2

0

2

4

6

8

10

12

14

0 5 10 15 20 25

Smolt weight (g)

% m

arin

e su

rviv

al

SoosUW

chinook

Site Weight % survival

UW 12.9 2.2

Soos 5.3 0.8

Size was related to survival of hatchery ocean-type Chinook salmon between hatcheries,

but not among years

So, body size does not strongly affect survival among years, but it does seem to play a role in variation in survival within years.

But, for a hatchery to release larger fish, they may hold them longer. What is the interaction between size and release date in controlling survival of salmon going to sea in a given year?

Survival of coho salmon from three size groups, differing from each other by 5 g

0

3

6

9

12

15

20-Apr 10-May 30-May 19-Jun

Date of release

Mar

ine

surv

ival

(%)

smallmediumlarge

Bilton et al. 1984; Morley et al. 1988. Quinsam River Hatchery.

Release date affected survival more than size. Why?

Smolt physiology? Ocean conditions?

Survival of Chinook salmon from the Columbia River declined later in the season, though the patterns varied among years (Scheuerell et al. 2009).

Other evidence that date may play a large role in survival at sea.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 0.05 0.1 0.15 0.2 0.25

Average survival of wild coho (5 rivers)

Aver

age

surv

ival

of h

atch

ery

coho

(20

popu

latio

ns)

1:1 ratio

In a given year, wild and hatchery survival rates were correlated, but wild coho salmon had

consistently higher survival rates in Washington (Beetz 2009)

Sometimes there are trends in survival (e.g., stream-type Chinook salmon smolts from the Snake River.

0

1

2

3

4

5

6

7

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

% s

mol

t to

adul

t ret

urn hatchery

wild

(Raymond 1988)

0.00

0.05

0.10

0.15

0.20

0.25

1970 1975 1980 1985 1990 1995 2000 2005

WildHatchery

Prop

ortio

n su

rviv

ing

at s

ea

Washington coho salmon also show trends over time, and the superior performance of wild fish

Beetz 2009

For a long time, many salmon biologists viewed the ocean as:

1) Not limiting salmon production

2) Not changing in any important ways

3) Not knowable anyway

But, in the early 1980s, variation in marine survival made people re-think all this…

Marine survival of Oregon hatchery coho salmon was positively related to an index of upwelling off the coast

0 100 200 300 400 500

0

2

4

6 8

1

0

12

Post-smolt survival (%)

Upwelling S. Mathews (1984)

Comparison of pink salmon caught in the Gulf of Alaska with coho catches in Washington, Oregon

and California (Francis and Sibley, updated)

0

20

40

60

80

100

120

1930 1940 1950 1960 1970 1980 1990

Pink

sal

mon

(mill

ions

)

0

1

2

3

4

5

6

Coh

o sa

lmon

(mill

ions

)

Gulf of Alaska pink salmon

WA, OR, CA coho salmon

Pink salmon catches in central and southeast Alaska seem to follow winter temperatures (November - March air

temperatures in Sitka, southeast Alaska).

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1930 1940 1950 1960 1970 1980 1990

Win

ter a

ir te

mpe

ratu

re

0

20

40

60

80

100

120

Mill

ions

of s

alm

on

temperaturepink salmon

We now understand that climate and ocean conditions are linked. There are “regimes” that favor salmon in

one part of the range but not others

High survival rates in the south, low in the north

High survival rates in the north, low in the south

Commercial catches of all salmon species in Alaska

0

50,000

100,000

150,000

200,000

250,000

1900 1925 1950 1975 2000

Cat

ches

(100

0s) o

f sal

mon

(Alaska Dept. of Fish and Game data)

Noakes et al. 1997. NPAFC Bull.

All nations, pink, chum, and sockeye catch

Yes, but what do the fish actually die of?

Presumably, the proximate cause of death is normally predation, though the fish may be weakened by disease, lack of stored energy, or poor seawater adaptation, and the vulnerability to predation may be extended if growth is slow.

But, who eats them?

There is no coastwide “enemy of salmon” but rather losses to many different species, depending on the size of the salmon and the region. Overall, little progress has been made on this issue.

Predators: Are harbor seals (for example) a significant predator on salmon?

(Olesiuk 1993)

How many seals are there? 12,990 prior to pupping and 15,810 afterwards.

How much fish do they eat? 1.9 kg or 4.3% body weight per day per seal

What is the composition of their prey?

Mostly Pacific hake from April to November and mostly Pacific herring from December to March in the Strait of Georgia

Harbor seal diet in the Strait of Georgia, B. C.

species tonnes % of total Pacific hake 4214 42.6 Pacific herring 3206 32.4 Pacific salmon 398 4.0 Midshipman 335 3.4 Lingcod 294 3.0 Other 1445 14.6 Total 9892 100%

Estimated mean smolt fork length of Chilko Lake sockeye salmon as outmigrants and surviving adults

Year Outmigrants Adults Probability

1971 81.7 (294) 82.3 (291) < 0.05

1976 88.8 (194) 89.2 (280) > 0.05

1977 95.7 (192) 97.3 (292) < 0.01

In general, fish that survived to adulthood had been larger as smolts than those that died, in a given year (Henderson and Cass 1991).

Life History Stage pink chum sockeye coho chinook steelhead cutthroat

female length (mm) 522 683 553 643 871 721 413

fecundity 1648 2876 3654 2878 5401 4923 1197

egg size (mg) 190 290 130 220 300 150 110

egg to fry survival 0.12 0.13 0.13 0.25 0.38 0.29

fry size (mm) 32 34 28 33 35 28 25

fry to smolt survival 0.26 0.17 0.10 0.14

smolt size (mm) 32 40 80 105 60-120 200 190

smolt to adult survival 0.03 0.01 0.1 0.1 0.03 0.1 0.2

adults per female 5.2 5.1 15.7 12.5 6.4 25.5

egg to smolt survival 0.02 0.02 0.10 0.01

adults per female 10.2 5.4 17.5 9.2

Sockeye salmon marine survival Koenings et al. 1993 CJFAS

70 90 110 130 150 170 Mean Smolt Length (mm)

Smol

t to

Adul

t Sur

viva

l (%

)

50 30 20 10

5 3 2 1