REFERENCE COPY 

Do Not Remove from the Library 

U. S. Fish and Wildlife Service 

IYQTI:?~~~ kVetlands Kesearch Center Biological Report -rR EL-82-4 82(11.88) 

January 1989 7G.3 Caiun Dome Boulevard 

La favette, Louisiana 70506 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes 

and Invertebrates (Pacific Northwest) 

PINK SALMON 

Fish and Wildlife Service 

Coastal Ecology Group 

Waterways Experiment Station 

U.S. Department of the Interior U.S. Army Corps of Engineers 
Biological Report 82(11.88) 

TR EL-82-4 

January 1989 

Species Profiles: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (Pacific Northwest) 

PINK SALMON 

Scott A. Bonar, Gilbert B. Pauley, and G. L. Thomas 

Washington Cooperative Fishery Research Unit 

School of Fisheries 

University of Washington 

Seattle, WA 98195 

Project Officer 

David Moran 

U.S. Fish and Wildlife Service 

National Wetlands Research Center 

1010 Gause Boulevard 

Slidell, LA 70458 

Performed for 

Coastal Ecology Group 

Waterways Experiment Station 

U. S. Army Corps of Engineers 

Vicksburg, MS 39180 

U.S. Department of the Interior 

Fish and Wildlife Service 

Research and Development 

National Wetlands Research Center 

Washington, DC 20240 
This series may be referenced as follows: 

U. S. Fish and Wildlife Service. 1983-19-. Species profiles: life histories 

and environmental requirements of coastal fishes and invertebrates. U. S. Fish 

Wildl. Serv. Biol. Rep. 82(11). U.S. Army Corps of Engineers, TR EL-82-4. 

This profile may be cited as follows: 

Bonar, S.A., G.B. Pauley, and G.L. Thomas. 1989. Species profiles: life 

histories and environmental requirements of coastal fishes and invertebrates 

(Pacific Northwest)--pink salmon. U. S. Fish Wildl. Serv. Biol. Rep. 82(11.88). 

U.S. Army Corps of Engineers, TR EL-82-4. 18 pp. 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, 

principal ly fish, of sport, commercial, or ecological importance. The profi 1 es 

are designed to provide coastal managers, engineers, and biologists with a brief 

comprehensive sketch of the biological characteristics and environmental 

requirements of the species and to describe how populations of 'the species may be 

expected to react to environmental changes caused by coastal development. Each 

profile has sections on taxonomy, 1 ife history, ecological role, environmental 

requirements, and economic importance, if appl icable. A three-ring binder is 

used for this series so that new profiles can be added as they are prepared. 

This project is jointly planned and financed by the U. S. Army Corps of Engineers 

and the U.S. Fish and Wildlife Service. 

Suggestions or questions regarding this report should be directed to one of 

the foll owing addresses. 

Information Transfer Specialist 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

NASA-Sl idel 1 Computer Complex 

1010 Gause Boulevard 

Slidell, LA 70458 

U. S. Army Engineer Waterways Experiment Station 

Attention: WESER-C 

Post Office Box 631 

Vicksburg, MS 39180 
CONVERSION TABLE 

Metric to U. S. Customary 

Multiply To Obtain 

millimeters (mm) 

centimeters (cm) 

meters (m) 

meters (m) 

ki 1 ometers (km) 

ki 1 ometers (km) 

inches 

inches 

feet 

fathoms 

statute miles 

nautical miles 

square meters (m2) 10.76 

square ki 1 ometers ( km2) 0.3861 

hectares (ha) 2.471 

square feet 

square miles 

acres 

liters (1) 

cubic meters (m3) 

cubic meters (m3) 

gal lons 

cubic feet 

acre-feet 

milligrams (mg) 

grams (g) 

ki 1 ograms (kg) 

metric tons (t) 

metric tons (t) 

ounces 

ounces 

pounds 

pounds 

short tons 

British thermal units 

Fahrenheit degrees 

ki 1 ocalories (kcal ) 

Celsius degrees (OC) 

U.S. Customary to Metric 

25.40 

2.54 

0.3048 

1.829 

1.609 

1.852 

inches 

inches 

feet (ft) 

fathoms 

statute miles (mi) 

nautical miles (nmi) 

mi 11 imeters 

centimeters 

meters 

meters 

ki 1 ometers 

ki 1 ometers 

square feet (ft2) 

square miles (mi2) 

acres 

square meters 

square kilometers 

hectares 

gal 1 ons (gal ) 

cubic feet (ft3) 

acre-feet 

liters 

cubic meters 

cubic meters 

ounces (02) 

ounces (02) 

pounds (lb) 

pounds (lb) 

short tons (ton) 

milligrams 

grams 

ki 1 ograms 

metric tons 

metric tons 

British thermal units (Btu) 

Fahrenheit degr,ees (OF) 

kilocalories 

Celsius degrees 
CONTENTS 

Page 

CONVERSION TABLE ............................. iii 

PREFACE .................................. i v 

ACKNOWLEDGMENTS .............................. v i 

NOMENCLATURE/TAXONOMY/RANGE ........................ MORPHOLOGY/IDENTIFICATION AIDS ...................... REASON FOR INCLUSION IN SERIES ...................... LIFE HISTORY ............................... Spawning ................................ Fecundity. Eggs. Alevins. and Fry .................... Marinestages .............................. GROWTH CHARACTERISTICS .......................... THE FISHERY ................................ ECOLOGICAL ROLE .............................. 9 

ENVIRONMENTAL REQUIREMENTS ........................ 10 

Water Temperature ............................ 10 

Salinity ................................ 11 

DissolvedOxygen ............................ 11 

Substrate ................................ 11 

Water Depth ............................... 11 

Water Velocity ............................. 12 

Turbidity ................................ 12 

LITERATURECITED ............................. 13 
ACKNOWLEDGMENTS 

We gratefully acknowledge reviews by Robert F. Donnelly and Steven S. 

Parker, both of the Fisheries Research Institute, University of Washington, 

Seattle. 
Figure 1. The pink salmon, showing extreme sexual dimorphism of the male (lower 

fish). Reprinted with permission of Scott and Crossman (1973). 

PINK SALMON 

Scientific name ........... Oncorh nchus 

gorbuscha (Wal baum) & 

Preferred common name.. ... Pink salmon 

Other common names.. .. humpback, humpback salmon, humpy (Scott and Crossman 1973) 

Class ..................... Osteichthyes 

Order .................... Salmoniformes 

Family ...................... Salmonidae 

Geographic range: Anadromous in rivers and small streams from northern 

California north to the arctic 

waters of Alaska, Canada, and the 

Soviet Union. Washington State 

appears to be at the southern end of 

the range for streams that support 

consistently exploitable spawning 

runs of pink salmon. Populations in 

Asia occur as far south as Hondo 

Island in Japan. Pink salmon have 

been introduced into the Great 

Lakes. Major rivers supporting pink 

salmon runs in the Pacific Northwest 

are shown in Figure 2. South of 

British Columbia, only a few rivers 

in the State of Washington that 

empty into Puget Sound support major pink salmon runs. Migration 

patterns of fish entering British 

Columbia and Washington waters are 

shown in Figure 3. Tagging studies 

have indicated that the majority of 

adult pink salmon destined for Puget 

Sound rivers migrate through the 

Strait of Juan de Fuca at the southern end of Vancouver Island, while 

those fish returning to southern 

British Columbia migrate primarily 

through the Strait of Georgia on 

the eastern side of Vancouver 

Island, with some returning through 

the Strait of Juan de Fuca (Figure 

3). 

MORPHOLOGY/IDENTIFICATION AIDS 

Morphology and identification aids 

are from Hart (1973) and Scott and 

Crossman (1973). Dorsal fin 10- 

15 rays; adipose small, slender, 

fleshy; anal 13-17 rays; pelvics 10 

rays, abdominal, with a free-tipped 
Marine dlstributlon: 

commonly 

abundant 

occasionally 

present 

MILES 

KILOMETERS 

1 .-- 

CALIFORNIA 

OREGON 

Figure 2. Major rivers in the Pacific Northwest supporting pink salmon runs. 
BR IT1 SII 

LUMI3 I A 

Figure 3. Principal migration routes (arrows) of pink salmon entering Puget 

Sound and British Columbia waters (from Washington State Department of Fisheries 

1959). 

fleshy appendage above insertion; margin of orbit. Males on spawning 

pectorals 15 rays. Cycloid scales migration develop a prominent high 

small, 150 to 205 on lateral line, hump immediately behind the head 

which easily distinguishes pink (Figure 1). Juveniles have no parr 

salmon from other species of salmon. marks, are blue to greenish along back 

Gill rakers 26 to 34 on first gill and silvery on sides. Distinguishable 

arch. Body elongate and somewhat lat- from other salmon by small scales. 

era1 ly compressed. 

Identification aids: Tai 1 (caudal REASON FOR INCLUSION IN SERIES 

fin) moderately forked. Numerous 

large, black, oval spots on upper Pink salmon are the most abundant 

sides and back and all of caudal fin. of the species of Pacific salmon. 

Upper jaw reaches beyond posterior They spawn in North American and Asian 
streams borderi ng the Pacific and Arctic Oceans. Their range in North America is extensive; they are the most 

numerous salmon in the commercial 

salmon fisheries with a very high rate 

of exploitation by Canadian, Japanese, 

Russian, and United States commercial 

f i shermen (A1 exandersdotti r and 

Mathi sen 1983). 

LIFE HISTORY 

Spawni ng 

Pink salmon have a 2-year life 

cycle, which is so invariable that 

fish running in odd-numbered cal endar 

years are effectively isolated from 

even-year fish so that no gene flow 

occurs between them (Larkin and Ricker 

1964; Hart 1973; Donnelly 1983). It 

is the simplest and least varied life 

history of any salmon. Because of 

this simplicity, the life cycle may be 

diagrammed as a circle with very 1 ittle overlap of the various stages 

(Figure 4). Usual age at maturity is 

2 years; however, 3-year-old specimens 

have been discovered on occasion (Anas 

1959; Turner and Bilton 1968; 

A1 exandersdotti r and Mathisen 1983). 

The salmon return to their stream 

of origin to spawn in the fall when 

the water temperature ranges from 8 to 

14 OC (Pritchard 1939; Hunter 1959), 

and usually enter the river on high 

water freshets (Pritchard 1939). Some 

pink salmon spawn several miles upstream from saltwater in a few river 

systems (Scott and Crossman 1973), but 

spawning general ly takes place either 

in freshwater close to the sea or in 

the intertidal zones. Pink salmon are 

considered the most specialized of the 

salmon in the genus .Oncorhynchus because they are the least dependent on 

freshwater, regularly spawning in the 

intertidal areas (Mi 11 er and Brannon 

1982; A1 exandersdotti r and Mathi sen 

1983). 

Males are larger than females. In 

general, larger fish, predominantly 

Dec , Jan 

Figure 4. Two-year life cycle of pink 

salmon from Kodiak Archipel ago. Dates 

may vary in different areas along the 

Pacific coast. Shaded areas show 

overlaps in time (after Donnelly 

1983). 

males, enter the streams first (Hart 

1973). Runs may be alternately large 

and small in consecutive years 

(Merrel 1 1962). Spawning usual 1 y occurs in late August through early 

October in mucn of the range (Sheridan 

1962). The female digs a depression 

in the gravel on the stream bottom in 

an area averaging 0.6 to 0.9 m in 

width (Wells and McNeil 1970), and in 

water with an average depth of 

0.15-0.53 m and velocity of 21-100 

cm/s (Col lings 1972). The tail is 

used to force water down on the gravel 

to remove fine sediments (Wickett 

1959a). A dominant male guards the 

female during the digging process, 

attacking competitors or intruders. 

Once the nest (redd) is dug, the 

female drops into the middle of the 

deepest part with a dominant male 

(Chebanov 1982), and the deposition of 

eggs and milt occurs. Up to six males 

have been recorded spawning with a 

single female (Wickett 1959a). 
Chebanov (1980) observed that, compared to larger males, smaller males 

showed less spawning activity and performed more movements within the 

spawning ground. After a brief milling, the spawning procedure is repeated upstream from the nest, and the new 

diggings cover the eggs in the previously dug redd. The female stays in 

the area, protecting her redds from 

other digging females (Chebanov 1980). 

When densities of spawners are high, 

nests are sometimes superimposed upon 

one another and the total number of 

eggs surviving is reduced (McNeil 

1967). 

Fecundity, Eggs, Alevins, and Fry 

Mature female pink salmon contain 

between 1,500 and 1,900 eggs 

(Pritchard 1937; Hart 1973). Fecundity is related positively to size 

(Foerster and Pritchard 1941). The 

eggs are large (about 6 mm in diameter) and orange-red. Both extragravel 

and i ntragravel chemical and physical 

(including hydraulic) factors control 

the success of egg survival. Water 

percolating through the gravel provides oxygen. During the incubation 

period, substantial mortality in. redds 

may result from freezing, flow fluctuations, dewatering, oxygen reduction, 

predation, and microbial infestation. 

In some instances, the total egg mortality may be as high as 75% to 90% 

(Krueger 1981). 

The length of the incubation period 

is dependent on water temperature 

(Carl et al. 1959). Under natural 

conditions in British Columbia, eggs 

hatch from late December to late February (Neave 1966). Once hatched, the 

alevins remain in the gravel for several weeks while the yo1 k sac is absorbed and incorporated into the body. 

Swimming fry emerge from the gravel in 

British Columbia streams as early as 

late February, but peak emergence in 

most localities occurs during April or 

May (Neave 1966). 

Pink salmon migrate to the sea soon 

after emerging from the gravel and 

spend most of their lives in saltwater. Fry were abundant in marsh 

area tidal channels of the Fraser 

River Estuary from March to June, with 

peak numbers occurring in April and 

early May (Levy and Northcote 1982). 

Unlike chinook and chum salmon fry 

which reside temporarily in the marsh 

before migrating into the Pacific 

Ocean, pink salmon fry appear to be 

only transient residents of the estuarine marsh area as they make their 

rapid and active migrations downstream 

(Levy and Northcote 1982). The fry 

swim at the surface, creating ripples 

during their downstream migration when 

cruising speeds of 0.6 ft/s are 

reached at temperatures of 6 to 7 OC 

(Wickett 1959b). 

Downstream migrations usually begin 

at night. Brett and Alderice (1958) 

reported that migrations rarely commenced before the incident light 

intensity had fa1 len below 0.1 foot 

candle at about 8: 30 to 8: 45 p.m. , with a peak migration between 9: 00 and 

10: 30 p.m. , and nearly no movement by 

12:30 a.m. A strong light avoidance 

reaction is shown initially by 

individual fry, but schooling fry 

acclimate to the light in about 15 

min and no longer avoid it (Hoar 

1956). 

Fry migrating to saltwater usually 

do not feed, but if the distance is 

great, they may feed on larval insects 

(McDonald 1960). Both the distance 

traveled by the fish and the constancy 

of direction are greater for large 

schools than for small ones (Hoar 

1958). The behavior of fry in large 

schools appears to be more orderly and 

precise than in small schools (Hoar 

1958). 

Early hatchery fry migrate downstream about 35 days ahead of late 

hatchery fry and about 55 days ahead 

of wild fry in British Columbia 

(Taylor 1980). Later migrating fry 

have considerably higher mari ne 
survival than early migrating fry, 

possibly because low water temperatures encountered by early migrating fry may slow their growth in 

the estuary and make them more 

vul herabl e to predators (Taylor 

1980). 

After 1 eavi ng freshwater , the young 

tend to remain close inshore during 

their first summer (Manzer 1956). In 

the intertidal regions, the young 

salmon prefer feeding in water of 

relatively low salinity. Preferred 

food includes various invertebrate 

eggs, amphipods, and copepods in Puget 

Sound (Gerke and Kaczynski 1972; 

Kaczynski et al. 1973), although other 

planktonic organisms are eaten el sewhere (Cooney et al. 1981). Adult pink 

salmon feed primari ly on amphipods, 

euphausi ids, and fish (LeBrasseur 

1966). Godin (1981a) conducted 

laboratory tests which showed that 

68% of the juvenile fish were most 

active during the day. Stomach 

analyses from fry showed that most 

feeding occurs during day1 ight 

hours in the littoral zone (Godin 

1981b). 

Migration in the sea is saltatory, 

with short periods of active migration 

interspersed with 1 onger periods when 

the fry do not migrate (Healey 1967). 

Theories for the control of marine 

migration incl ude movement toward 

higher sal i ni ties (Baggerman 1960; 

McInerney 1964; Leggett 1977) and the 

use of tidal flow and food gradients 

(Hurley and Woodall 1968; Leggett 

1977). The fish begin moving offshore 

in late summer (Manzer 1956), in a 

manner that appears to be gradual or 

irregular, and 1 eave the young-ofthe-year at a distance of 6-12 mi from 

the nearest land in the fall (Neave 

1966). 

Marine Stages 

At the beginning of their ocean 

migrations, pink salmon from Washington, Oregon, and Southern British Columbia move northward from their 

streams of origin in a narrow belt 

along the coast (Hart 1973). Substantial numbers of fish from British 

Columbia stocks move up to 500 mi 

offshore, migrating rapidly to attain 

that distance (Hart 1973). Tidal currents may strongly influence the direction of movement, as well as other 

orientation cues (Leggett 1977). 

Stocks from southern locations tend to 

enter the ocean first, followed by 

stocks from more northern and western 

locations as the season progresses. 

In winter and early spring, the distribution of stocks is more southerly 

in the western North Pacific than in 

the eastern North Pacific. This may 

reflect the influence of colder waters 

in the western subarctic gyre (Royce 

et a1 . 1968; Burgner 1980). Ocean 

migrations of pink salmon vary greatly 

between populations from different 

geographical areas; the migration of 

stocks of the eastern North Pacific is 

much more restricted than that of other stocks (Burgner 1980). 

The vertical distribution of pink 

salmon in the ocean is not we1 1 known. 

Gillnet and longline catches on 

which knowledge of horizontal distribution is based are usually made 

within 6 to 7 m of the surface. In 

the Gulf of Alaska, some fish have 

been caught at depths of 24 to 36 m 

(Manzer and LeBrasseur 1959; Neave 

1953, 1966). 

After spending about 18 months at 

sea, adults return to the spawning 

streams in predictable and highly 

segregated even-numbered-year and 

odd-numbered-year runs. Salmon spawning migrations are thought to be 

guided by environmental cues such as 

01 faction, currents, temperature, and 

salinity, as well as by celestial 

navigation or magnetic orientation 

(Royce et al. 1.968; Leggett 1977; 

Brannon 1982), but the exact cause 

of the migrations is not known. The 

timing of the migrations is variable. 

The rate of straying is much higher 

in pink salmon than in other species 

of salmon. This straying could con- 
stitute a survival strategy that pink 

salmon have evolved either to recol onize streams which have lost a year 

class due to environmental catastrophe 

or to ensure that all fish headed for 

an uninhabitable stream are not eradicated. This straying mechanism could 

have evolved with the normal tendency 

of pink salmon to spawn in small, 

environmental ly unstable streams. 

Leggett (1977) and Brannon (1982) 

discussed in detail the numerous 

theories that have been advanced to 

explain salmonid homing. 

GROWTH CHARACTERISTICS 

The use of scale annulus formation 

to determine age in pink salmon has 

been discussed by Pearson (1966). 

When the fry hatch and leave the substrate, they range from 3.2 to 3.8 cm 

in total length from the tip of the 

snout to the fork of the tail and 

weigh approximately 0.3 g (Pri tchard 

1944). The fry feed relatively 

little, if at all, during their downstream migration and thus leave the 

streams at about this same size 

(Pri tchard 1944). 

During the first 30-day period at 

sea (beginning in August or September), the fry increase in weight by a 

factor of 6 (LeBrasseur and Parker 

1964). During their first 40 days at 

sea, pink salmon grow to about 8 cm 

and by the following March reach a 

length of about 33 cm (Parker 1968). 

During the last spring and summer in 

the sea, growth is rapid from about 

0.5 kg up to an average weight of between 2 and 4 kg (LeBrasseur and Parker 1964). 

THE FISHERY 

The pink salmon is less desirable 

than other Pacific salmon in commercial and sport catches, because of its 

small size, pale flesh, and flaccid 

texture. However, its status as a 

food item and sport fish is increasing. The history of the pink salmon's importance in the early Pacific 

Northwest fishery was given in an 

overview by Cobb (1911). Early salmon 

canneries, establ ished in the Seattle 

area in the 18701s, occasionally 

packed pink salmon. 

Hoar (1951) summarized the pink 

salmon fishery for 1917 to 1947. The 

pink and the chum salmon, referred to 

as autumn salmon, were considered less 

desirable species on the market than 

coho, chinook, and sockeye salmon because their flesh was soft and pale. 

At the beginning of World War I, a 

substantial increase occurred in the 

fishery because of wartime food requi rements and the temporary decrease 

in the Fraser River catch of other 

salmon due to the rock slide at Hell's 

Gate in British Columbia that blocked 

the Fraser River. Since that time, 

the pink salmon has been increasing in 

importance. The fish are usually taken by purse seines or gill nets, but 

troll fishing for pink salmon has been 

increasing in importance since 1950 

(Di Donato 1968). The primary reason 

for the increased troll catch is an 

expanded market for pinks in the 

fresh- and frozen-fish markets, in 

which fish caught by trolling are preferred over those taken in nets (Di 

Donato 1968). From 1935 to 1963, the 

average commercial catch of pink salmon in Washington State generally increased (Di Donato 1968). Washington 

commercial pink salmon landings in 

number of fish by gear type (Table 1) 

indicate the predominance of the 

strong odd-year runs in Washington 

State. 

Di Donato (1968) indicated that the 

Puget Sound region was the southern 

geographic limit of streams supporting 

major pink salmon runs in the eastern 

North Pacific. Significant pink 

salmon runs are present only in oddnumbered years in Puget Sound rivers 

and in the Fraser River, which is the 

major pink salmon producing river in 

southern British Col umbia (Di Donato 

1968). In contrast, the more northerly streams of British Columbia and 

Alaska have strong annual runs of pink 
Table 1. Commercial Landings of number of pink salmon in Washington State by 

gear type (data from Washington State Department of Fisheries 1983). 

Gill Purse Reef Other Total 

Year Troll net seine net gears fish 

salmon in both odd- and even-numbered 

years (Manzer et al. 1965; Donnelly 

1983), while Bristol Bay, Alaska, has 

essential ly just even-numbered year 

runs (R. Donnelly, 1986, Fish. Res. 

Inst., Seattle; pers. comm.). The 

cyclical nature of the dominant oddyear pink salmon runs in Washington 

State can be observed in the commercial catches for those years (Figure 

5). 

Not until the late 1950's was it 

realized that pink salmon would take 

artificial bait. Since then, their 

popularity as sport fish has increased. From 1957 to 1961, the 

estimated annual sport catch in 

British Columbia varied from 1,000 to 

37,000 fish (Scott and Crossman 

1973). The sport fishery for pink 

salmon in Puget Sound, Washington, 

has been extremely productive in 

recent years, perhaps stimulated by 

extremely liberal catch limits set 

by the Washington Department of 

Fisheries. 

Pink salmon fisheries management is 

made complex by user-group allocations 
SOCKEYE CHINOOK CHUM PINK COHO 

1981 - TOTAL POUNDS 47,057,650 

1982 - TOTAL POUNDS 49,512,433 

Figure 5. Cyclical nature of the commercial pink salmon catch 

relative to other salmon in Washington State is shown for oddand even-numbered years that yielded 42% and 0% pink salmon, 

respectively (modified from Washington State Department of 

Fisheries 1983). 

and mixed-stock fisheries. Optimum 

yield is the desired goal. Successful 

management requires effective data 

systems, advance planning, we1 1 - established spawning escapement objectives, dependable predictions of 

population size, and recognition of 

practical differences between recreational and commercial fisheries 

(Wright 1981). 

Ocean fisheries are managed by a 

catch quota system, while fisheries in 

terminal areas are managed by subtracting escapement goals from preseason run forecasts and inseason run 

updates. After subtraction of the 

ocean catches and escapement goals, 

the estimated number remaining gives 

the total allowable harvest, which is 

a1 located among user groups. The 

Washington Department of Fisheries and 

the various tribal entities have 

worked much more closely toward a 

unified salmon management plan due 

to the Boldt Decision in 1974 (Clark 

1985). 

ECOLOGICAL ROLE 

When juvenile pink salmon enter 

the estuarine environment, they feed 

near the surface, primarily during 

daylight hours (Godin 1981a). Stomach 

analyses of pink salmon in British 

Columbia showed that maximum mean prey 

biomass occurred near or at dusk 

(Godin 1981a). Apparently, once a 

fish's stomach is full, spontaneous 

feeding resumes after only 15% of the 

stomach contents have been evacuated 

(Godin 1981b). Juvenile pink salmon 

quickly adapt to feeding on pelagic 

copepods and other epibenthic and 

planktonic organisms (Gerke and 
Kaczynski 1972; Bailey et al. 1975; 

Cooney et al. 1981). Food of juveniles in protected waters such as 

Chatham Sound, Alaska, and Puget 

Sound, Washington, includes harpacticoid copepods, copepod nauplii, invertebrate eggs, tuni cates, and barnacle 

larvae (Manzer 1969; Gerke and 

Kaczynski 1972; Kaczynski et al. 1973; 

Simenstad et al. 1980; Godin 1981b). 

Pink salmon co-occurring with juvenile 

chum salmon of approximately the same 

size in Hood Canal had an overlap in 

dietary items that approached 75% 

(Simenstad et al. 1980). The estuarine residence time of juvenile pink 

salmon varies from 4 to 18 weeks 

(Simenstad et al. 1982). Allen and 

Aron (1958) found the preferred food 

of pink salmon in the ocean to be 

amphipods, supplemented by fish, 

euphausiids, squid, and crustacean 

larvae. However, differences were 

noted in the diets of fish close to 

shore versus those of fish far from 

shore: for fish from inshore waters, 

amphipods were the most important and 

crustacean larvae ranked second in 

importance; for fish from offshore 

waters, copepods and euphausiids were 

the dominant food items. Pink salmon 

appeared to select 1 arger food i tems 

as they moved further offshore (Allen 

and Aron 1958). It has been hypothesized that appreciable differences in 

average size of individual pink salmon 

in different years are probably due, 

in part, to differences in feeding 

conditions (Davidson and Vaughan 1941; 

Neave 1953). 

Competition and predation can have 

significant effects on the pink salmon 

populations. Young pink salmon fry 

are preyed upon by a variety of stream 

fishes, including Do1 ly Varden (xvelinus malma), cutthroat trout (Salmo 

cl arki ) , rainbow trout (Salmo gai rdneri), young coho salmon (Oncorhynchus 

kisutch), northern squawfish (Ptychochei 1 us oregonensi s) , and sculpi ns 

(Cottus spp.) (Hunter 1959; Hart 1973; 

Scott and Crossman 1973; Hargreaves 

and LeBrasseur 1985). Kingfishers, 

mergansers, other predaceous birds, 

and mammals a1 so probably account for 

some amount of predation (Hart 1973; 

Scott and Crossman 1973; Simenstad 

et al. 1982). Infestations of leeches 

on eggs and fry can also significantly 

increase mortal i ty (Earp and Schwab 

1954). Predation by and competition 

with juvenile coho salmon was considered the main contributor to early 

sea mortality in pink salmon according 

to Parker (1971). Year1 ing Coho 

apparently prey selectively on young 

pink salmon, even in the presence of 

chum salmon that are both significantly smaller and more abundant than 

the pink salmon (Hargreaves and 

LeBrasseur 1985). Early sea mortality 

can also be associated with predation 

by certain species such as herring 

(Thorstei nson 1962). Adults at sea 

are preyed upon by humans, marine 

mammals, and, to a lesser extent, 

large fishes. Upon returning to the 

rivers, pink salmon are preyed on by 

bears and humans. 

ENVIRONMENTAL REQUIREMENTS 

Water Temperature 

According to Rei ser and B jornn 

(1979), the optimum water temperatures 

for pink salmon spawning range from 

7.2 to 12.8 OC. Pink salmon eggs tolerate long periods of low temperature, 

provided the initial temperature was 

above 6.0 OC when embryogenesis began 

and initial development of the embryo 

progressed to a stage that was tolerant of colder water (Combs and Burrows 

1957; Combs 1965; Reiser and Bjornn 

1979). Incubation temperatures for 

successful development range from 4.4 

to 13.3 OC (Reiser and Bjornn 1979). 

Extremely cold water and low air 

temperatures cause mortality among 

incubating eggs and fry when ice 

formation reduces water interchange 

(Neave 1953; McNeil 1966; Reiser and 

B jornn 1979). 

Adult pink salmon are cold-water 

fish with a preferred temperature 

range of 5.6 to 14.6 OC, an optimal 
temperature of 10.1 OC, and an upper 

1 ethal temperature of 25.8 OC (Rei ser 

and Bjornn 1979). The relatively high 

stream temperatures (17 OC) and low 

dissolved oxygen levels associated 

with drought conditions have apparently killed many mature adult pink salmon in Alaskan streams (Krueger 1981). 

Salinity 

Juvenile pink salmon encounter 

a wide range of salinities in their 

migrations. Salinity gradients are 

thought to play a part in salmon migrations (Baggerman 1960; McInerney 

1964). Noerenburg (1963) estimated 

that over 50% of the pink salmon 

spawning activity in Prince Will iam 

Sound, Alaska, occurs in intertidal 

areas. Bailey (1969) showed that developing pink salmon eggs and alevins 

can be adversely affected when exposed 

to some high intertidal salinities. 

Dissolved Oxygen 

Dissolved oxygen (DO) is supplied 

to developing eggs and alevins within 

the redd by intragravel flow. Dissolved oxygen level within the redd 

is influenced by the dissolved oxygen 

in the stream, the rate of intragravel 

water flow, and the biological demand 

for oxygen in the immediate area. For 

incubation of salmonid eggs, concentrations at or near saturation with 

temporary reductions to levels no lower than 5.0 mg/l are optimal (Reiser 

and Bjornn 1979). However, DO levels 

exceeding 6.0 mg/l are required for 

successful development of pink salmon 

, eggs and alevins (Bailey et al. 1980). 

Oxygen consumption generally increases 

as embryo development progresses, and 

DO generally decreases in an area supporting large numbers of eggs or 

a1 evi ns (Bai ley et a1 . 1980). Low DO 

concentrations may result in a variety 

of fry abnormalities (Silver et al. 

1963; Shumway et al. 1964; Reiser and 

Bjornn 1979). During the latter part 

of incubation, reduced DO can cause 

premature hatching (Alderdice et al. 

1958; Bailey et al. 1980). Growth 

rate, food consumption, and efficiency 

of food utilization by juvenile salmon 

all declined at lowered DO (Reiser and 

Bjornn 1979). Reduced DO concentrations can significantly hamper the 

swimming performance of migrating 

adult salmonids (Jones 1971; Reiser 

and Bjornn 1979). In addition, mortalities may occur in adults when low 

DO is combined synergistically with 

high temperatures (Krueger 1981). 

Substrate 

The diameter of gravel that composes the substrate for spawning pink 

salmon ranges from 1.3 to 10.2 cm 

(Lucas 1959; Col linqs 1974). Pink 

salmon spawn over a variety of substrate material s. The size, shape, 

density, and embeddedness of the material, current velocity, water depth, 

and densities of fish can influence 

substrate selection. Successful fry 

emergence is physical ly hindered by 

excessive amounts of sand and silt 

in the gravel, which also limit the 

percolation of water with its DO 

content (Reiser and Bjornn 1979). 

Hourston and MacKinnon (1957) suggested that very small gravels made ideal 

pink salmon spawning areas. No differences in size or time of return of 

adults could be traced to the nature 

of the gravel environment from which 

they came (Bai 1 ey et a1 . 1976). 

Eggs and developing alevins are 

i nf 1 uenced by the substrate. Productive pink salmon streams generally 

contained less than 5.0% by volume of 

fine sediments (t0.8 mm), whereas less 

productive streams had 15.0% or more 

fines in the substrate (Krueger 1981). 

Water Depth 

Water depth selected by pink 

salmon is determined by current velocity and substrate type. Preferred 

water depths for spawning pink salmon 

in selected Washington State streams 

ranged from 0.2 to 0.5 m (Collings 

1974). Hourston and MacKi nnon (1957) 

studied water depth preferences in a 
spawning channel and found that the 

first fish that entered the channel 

chose sites with mean depths of 0.4 m 

and subsequent fish occupied progressively shallower mean depths. It appears that in nature these shallower 

depths are used even though they are 

less than optimal situations (Krueger 

1981; Wilson et al. 1981). 

Water Velocity 

A1 though several current vel ocities are suitable for pink salmon 

spawning, the preferred velocities 

range from 21 to 101 cm/s (Coll ings 

1974). Pink salmon in the Terror 

River, Alaska, spawned in areas with 

current velocities ranging from 0.19 

to 0.66 m/s, but the preferred spawning velocities ranged from 0.35 to 

0.47 m/s (Wilson et al. 1981). Flow 

regimes can affect developing pink 

salmon eggs and alevins through either 

mechanical damage, temperature 

changes, or reduced intragravel dissolved oxygen levels (McNeil 1966; 

Reiser and Bjornn 1979; Krueger 

1981). 

The high current velocities associated with high stream discharges 

sometimes exceed the swimming capabilities of pink salmon and prevent upstream migration. However, pink 

salmon can negotiate current velocities up to about 2.1 m/s (Krueger 

1981). Upstream migrations of adults 

can be hampered by either too little 

or too much stream flow (Wickett 1958; 

Reiser and Bjornn 1979; Krueger 1981). 

Turbidity 

According to Rei ser and B jornn 

(1979), migrating salmon avoid or 

cease to migrate in waters with very 

high silt loads (4,000 mg/l). Turbid 

water absorbs more radiation than 

clear water, thus possibly resulting 

in temperature barriers to upstream 

migration. Increased turbidity a1 so 

may cause osmoregul atory problems i n 

young fish by interfering with gill 

function. This results in delayed 

entry into seawater and increased predation on the estuarine population 

(Kehoe 1982). Eggs may be suffocated 

by the increased deposition of fine 

sediment and adults may suffer from 

impaired oxygen transport, decl i ne in 

nutritional intake, and physical damage to the gill filaments by abrasion 

(Rivier and Seguier 1985). 
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Hunter, J.G. 1959. Survival and production of pink and chum salmon in a Leggett, W.C. 1977. 'The ecology of 

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downstream migration to freshwater 

and saltwater nursery areas. J. 

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McInerney, J. E. 1964. Salinity preference, an orientation mechanism in 

salmon migration. J. Fish. Res. 

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McNeil, W.J. 1966. Effect of the 

spawning bed environment on reproduction of pink and chum salmon. 

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McNeil, W. J. 1967. Randomness in 

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1629-1632. 

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during early ocean residence. Fish. 

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Chatham Sound and adjacent waters. 

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1959. Further observations on the 

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fishes in a British Columbia inlet. 

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50172 -101 

~orthwest)--pink Salmon 1 - 

REPORT DOCUMENTATION I 

PAGE I Bioloaical rie~ort 82( 11.88) * 4. Title and Subtitle 1 5. Repor( Date 

Species Profiles: Life Histories and Environmental January 1989 

?. Authods) 8. Performing Organization Rept. Nc 

Scott A. Bonar, Gilbert B. Pauley, and G. L. Thomas 

9. Performing Orsanixation Name and Address 

2. I 3. Rnp~ent's Accession NO, 

Reauirements of Coastal Fishes and Invertebrates (Pacific 

Washington Cooperative Fishery Research Unit 

University of Washington 

Seattle, WA 98195 

.S 

12. Sponsoring Organization Name and Address 

U.S. Dep. of the Interior U.S. Army Corps of Engineers 

Fish and Wildlife Service Waterways Experiment Station 

National Wetlands Research Center P. 0. Box 631 

Washington, DC 20240 Vicksburg, MS 39180 

1'; Contract'c) or Grant'") NO. 

(GI 

13. Type of Repor( L Period Coverec 

-- IS. Supplementary Notes 

*U.S. Army Corps of Engineers Report No. TR EL-82-4 

16. Abstract (Limit: 200 word.) 

Species profiles are literature summaries of the taxonomy, morphology, range, life 

history, and environmental requirements of coastal aquatic species. They are designed 

to assist in environmental impact assessment. The pink salmon, often cal led humpback 

salmon or humpy, is easily identified by its extremely small scales (150 to 205) on the 

lateral line. They are the most abundant of the Pacific salmon species and spawn in 

North American and Asian streams bordering the Pacific and Arctic Oceans. They have a 

very simple two-year life cycle, which is so invariable that fish running in oddnumbered years are isolated from fish running in even-numbered years so that no gene 

flow occurs between them. Adults spawn in the fall and the young fry emerge in the 

spring. The pink salmon is less desirable in commercial and sport catches than most 

other salmon because of its small size and its soft pale flesh. The Puget Sound region 

of Washington State is the southern geographic limit of streams supporting major pink 

salmon runs in the eastern North Pacific. Pink salmon runs are presently only in oddnumbered years in this region. Optimum water temperatures for spawning range from 7.2 

to 12.8 OC. Productive pink salmon streams have less than 5.0% by volume of fine 

sediments (50.8 mm). 

17. Document Analysis a. Descrlpton 

Estuaries Temperature Life cycle 

Fisheries Sediments Growth 

Salmon Suspended sediments Oxygen competition 

Salinity Feeding habits Animal migrations 

b. 1dentlfienlOpen.Ended Terms 

Pink salmon Life history Predators 

Humpback salmon Spawning Competitors 

Oncorhynchus gorbuscha Temperature requirements 

Sal i nity requirements 

.a Availability Statement / 19. Secur~ty Class (This Repom 1 21. No. of Pages 

Oepertment of Commerce 

Unclassified 

Unlimited 

Unclassified 

18 -- 

22. Price 

ee ANSI-239.18) OPTIONAL FORM 272 (4-77 

(Fornwrly NTIS35) 
TAKE PRIDE 

in Amerzcd 

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