■n

ALASKA'S
FISHERY

RESOURCES

UNITED STATES DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

BUREAU OF COMMERCIAL FISHERIES

Fishery Leaflet 619

UNITED STATES DEPARTMENT OF THE INTERIOR
U.S. Fish and Wildlife Service

BUREAU OF commercial FISHERIES

Alaska's Fishery Resources
The Pink Salmon

By
JACK E. BAILEY

Fishery Leaflet 619
Washington, D. C.
March 1969

CONTENTS

Page

Introduction 1

Description 1

Geographic distribution and abundance 1

Natural history 1

Spawning 2

Survival 3

Food and growth 5

Migrations 5

Economic importance 5

Research and management 6

Publications on pink salmon 7

m

ABSTRACT

Pink salmon, Oncorhynchus gorbuscha, also called humpback salmon, are the most abundant
of the Pacific salmon in Alaska. Alaska production of pink salmon has an average wholesale value
of $28 million and constitutes more than half of the total North American catch. Female pink
salmon carry about 2,000 eggs each and spawn in late summer or early fall. The resulting fry emerge
the following spring and migrate directly to salt water. They spend 1 year at sea and return as
2-year-olds to spawn and die in their native stream. Alaskan pink salmon usually spawn only a short
distance from the sea; many even spawn in intertidal streambeds. Fewer than 25 percent of the
young survive from the time of spawning until the time of emergence from the gravel. Similar low
survival rates prevail during the estuarine and oceanic portions of the life cycle. Pink salmon are
just over 1 inch long when they enter the sea, but they grow to an average length of about 20
inches and weigh about 4 pounds as adults. Research biologists of several agencies assist fishery
managers by determining the migration paths and the factors that affect abundance of pink salmon.

IV

ALASKA'S FISHERY RESOURCES - THE PINK SALMON

By

JACK E. BAILEY, Fishery Biologist

Bureau of Coinmercial Fisheries Biological Laboratory

Auke Bay, Alaska 99821

INTRODUCTION

Pink salmon, Oncorhynchus gorbusclia, are called the
bread and butter fish of the Alaskan salmon industry
because they are the most consistently abundant of the
five Pacific salmons in Alaska-pink, sockeye, chinook,
coho, and chum. The name "pink" comes from the deli-
cate color of the tlesh of the pink salmon, which is also
known as "humpy" or "humpback" salmon because of
the hump that develops on the back of the spawning
male (fig. 1).

DESCRIPTION

As with all salmon, the pink salmon change their ex-
ternal color as they mature. In the late spring just after
the fry emerge from the streambed, they have a general
silvery appearance and their backs are often deep blue to
green. They are easy to distinguish from other salmon
fry because they do not have the dark bars or spots,
called parr marks, that are prominent on the sides of
other salmon fry, such as the chum salmon, which are
found most frequently with pink salmon fry (fig. 2).
During the first 3 months after they enter the ocean, all
young Pacific salmon are silvery and have a similar gen-
eral appearance, but experts can recognize pink salmon
by their small and numerous scales and by subtle differ-
ences in shape and color and in internal structures. In
about Augusi of their first year in the sea, juvenile pink
salmon develop on tiieir backs and tails the large dark
spots that are characteristic of the adults.

At the end of their second summer in the ocean when
pink salmon begin their migration back to fresh water,
they have further changes in color and body shape. The
silvery sheen is replaced by dark sides and a white belly,
and the dark spots on the back and tail become more
prominent. At this time the males develop their pro-
nounced hump, as well as an elongated hooked jaw with
large sharp teeth.

GEOGRAPHIC DISTRIBUTION AND
ABUNDANCE

Pink salmon occur in streams from California to the
Arctic Ocean on the North American side of the Pacific
Ocean and from the Arctic Ocean south to Hokkaido
Island of northern Japan on the Asian side. Their oceanic
distribution extends from North America to Asia north
of the 40th parallel through the Bering Strait into the
Arctic Ocean.

Although several attempts have been made to trans-
plant pink salmon to waters outside their natural range,
no new important fishery has been established. The
United States planted them in rivers in Maine, the Rus-
sians in tributaries of the Barents and White Seas of
northern Europe, and the Canadians in tributaries to
Hudson Bay and in rivers in the Maritime Provinces of
eastern Canada. None of these efforts resulted in runs
that survived more than a few cycles.

Although pink salmon do not usually complete their
life cycle in fresh water, an accidental release of several
hundred fry resulted in a population that perpetuated
itself for a few cycles in Lake Superior.

The geographic distribution tells us nothing of the
importance of a fish-it is the abundance that determines
its value to the fishermen, and the best available measure
of the abundance of pink salmon is the commercial catch.
The catch in Asia is about twice that in North America.
Puget Sound is the southern limit and Bristol Bay the
northern limit of commercially important runs in North
America. Alaska produces more than half of the North
American total, and southeastern Alaska produces about
half of Alaska's total catch. Other important pink salmon-
producing areas in Alaska are Prince William Sound, Cook
Inlet, Kodiak Island, and the south side of the Alaska
Peninsula.

NATURAL HISTORY

The life of the pink salmon begins in late summer or
early fall when the fertilized eggs are deposited in the
gravel and start to develop. These eggs hatch in mid-
winter; the fry emerge from the streambed in the spring
and migrate directly to sea. There they spend 14 or 15
months feeding and growing before they return to their
home stream to spawn and die. The life cycle of the pink
salmon is illustrated in figure 3, and some of the biologi-
cal characteristics of this species are compared with those
of the other Pacific salmon in table 1 .

Pink salmon have the shortest and simplest life his-
tory of any Pacific salmon. Because they have a 2-year
life cycle and return to their native streams to spawn,
two genetically distinct lines occur in each stream. The
lines are called "even-" or "odd-year" on the basis of the
year in which the adults spawn. Differences in the num-
ber and in the size of the fish in the two lines have been
the subject of speculation for many years. In some areas,
only one line spawns in significant numbers, leaving fish-
erman with few or no fish in an "off year. For example,

Figure 1. -Mature pink salmon-male (upper), female (lower).

in southern British Columbia and Puget Sound, runs large
enough for profitable commercial fishing occur only in
odd years. Conversely, in western Alaska since 1954, the
even-year runs have been the larger. Fortunately the
major pink salmon-producing areas of Alaska do not suf-
fer from this type of off-year scarcity.

Spawning

Pink salmon usually ascend streams only short dis-
tances to spawn, although in British Columbia and Cali-
fornia some migrate more than 200 miles from the sea to
the spawning grounds, and in Asia they migrate up to
400 miles from the sea. In Alaska, pink salmon typically
spawn in the lower reaches of short coastal streams,
although many use the intertidal areas of these streams,
where the eggs are alternately bathed by fresh and brack-
ish water as the tides ebb and tlow (fig. 4). In Prince Wil-
liam Sound, for instance, between 50 and 75 percent

of the pink salmon fry are produced in intertidal zones.

Spawning usually begins in August or September when
stream temperatures are about 50 F. Water tempera-
tures near freezing are common in winter. The spawning
season and the time of fry emergence are related to the
temperature regimes of the streams. Pink salmon tend to
spawn earlier in colder streams and later in warmer ones.
The eggs hatch from 3 to 5 months after they are spawned,
but the try remain in the gravel until .April or May.

To prepare the spawning nests, the females dig pock-
ets, called redds, in riflles with gravel bottoms. The redds
are from 4 to 10 inches deep, depending on the size of
the female and the velocity of the water current. After
she has dug her redd, the female releases her eggs a few
at a time and the male releases a cloud of milt containing
sperm which fertilize the eggs as they fall to the bottom
of the redd. Egg laying is alternated witli more digging
at the upstream face of the redd so that each release or
cluster of eggs is quickly covered with sand and gravel,

Figure 2. -Pink and chum salmon fry that have just emerged from the streambed. The pink salmon are distinguished by their
smaller size and the lack of the parr marks that are noticeable on the backs of the chum salmon fry. In these live fish the
fins arc nearly transparent because they are very thin and unpigmented.

and a new egg pocket is formed to receive the next clus-
ter. Sand and gravel protect the eggs from sunlight, floods
and predators, and the female protects them from being
dug up by other females who are digging their own redds.

Pink salmon are somewhat inefficient at burying their
eggs in the streambed; some of this inefficiency can be
traced directly to the density of the spawners. When too
many females are present, some frequently dig up eggs
that are deposited by other females, and some may not
be able to deposit all of their eggs before they die.

Males and females both die soon after they spawn.

Survival

A mature female pink salmon usually has about 2,000
eggs, but if only two of these survive to return as mature
spawners the population will be perpetuated. The life
history of pink salmon occurs in three physically and

biologically distinct environments-streams, estuaries, and
the ocean-and biologists have studied survival in each
environment. In the stream less than 25 percent of the
eggs survive from the time of spawning to the time of
emergence from tiie gravel. The principal causes of the
death of salmon eggs are ( 1 ) digging in the redds by other
females, (2) low oxygen supply because of low stream-
flows or impairment of water circulation within the
streambed, (3) dislodgment of eggs by Hoods, (4) freez-
ing of eggs during periods of severe and prolonged cold,
and (5) predation by other fish. Less is known about
survival in the other two environments, but indications
are that about three-fourths of the fry entering the estu-
ary are lost before they reach the ocean and that of those
reaching the ocean, about three-fourths die before they
attain maturity. Predation is believed to be the principal
cause of death in the estuary and at sea.

MATURING FISH, 10-12 MONTHS OLD

IN OPEN OCEAN, ABOUT 15 INCHES

LONG

JUVENILE FISH, 4 MONTHS OLD
IN COASTAL WATERS, 6-9 INCHES
LONG

Figure 3.- Life cycle of pink salmon.

Table 1. -General life history features of the five species of Pacific salmon in Alaska (Exceptions
to these general descriptions occur frequently)

Time spent

in fresh

Species

water after

Time

Year of

Average

Average

of

Fresh-water

emergence

spent

life at

weight

eggs per

salmon

habitat

from gravel

at sea

spawnmg

of adults'

female

Years

Pounds

Thousands

Pink

Short streams

Usually less
than I day

1

2

4

2.0

Chum

Short and long
streams

Less than
1 month

2-t

3-5

8

3.0

Sockeye

Short streams
and lakes

12-36 months

1^

3-6

6

3.5

Coho

Short streams
and lakes

12-24 months

1-3

3^

9

3.5

Chinook

Large rivers

3-12 months

1^

3-6

20

4.0

'Weight of whole or round fish. Source: Int. North Pac. Fish. Comm., Bull. 12, p. 48.

Food and Growth

Pink salmon fry grow slowly while they are buried in
the streambed and are just over 1 inch long when they
migrate to sea. While in the streambed, they obtain nour-
ishment from the yolk of the egg, which contains a bal-
anced "diet" of protein, carbohydrates, vitamins, and
minerals. Growth increases rapidly after the fish reach
the sea and its abundant supply of plankton. Pink salmon
select their food by sight and swallow it whole. As they
grow larger, they feed on progressively larger animals,
until squid and other fish are included in their diet. In
the extensive estuaries of southeastern Alaska, they may
reach a length of 6 to 9 inches before they move into
the open ocean. When they return to fresh water several
months later, their usual average length is about 20 inches,
and their average weight is about 4 pounds. Mature pink
salmon do not feed in fresh water.

Migrations

Pnik salmon fry emerge from the gravel at night and
begin their migration to the sea. When the distance to
the sea is short, they reach the estuary of the stream be-
fore dawn. In the first few days in the estuary they form
schools near the surface of the water and migrate along
shore. At this stage they move with surface currents and
are carried out of the estuary into the ocean in a few
days to several weeks.

It is not known how salmon are able to find their way
from the estuary to the ocean feeding grounds and to
return to their home stream. According to one theory,

they continue to move more or less passively with the
prevailing surface currents, which carry them in a roughly
circular path out into the North Pacific Ocean and back
toward their home stream. Most biologists believe that as
the fish approach the coast again, a keen sense of smell
and a good memory enable them to find their home
stream by its characteristic odors. This theory does not
explain, however, how those American and Asian salmon
stocks that intermingle at sea are able to find their way
back to their home continents.

ECONOMIC IMPORTANCE

Salmon fishing is the largest commodity industry in
Alaska, and pink salmon is the most valuable species
(table 2).

Most pink salmon are caught in coastal waters by
purse seiners (fig. 5), but a small percentage of the com-
mercial catch is taken by gill nets. Commercial trollers
and sport fishermen catch a few pink salmon while fish-
ing for Chinook and coho salmon. The fish are generally
canned in shore-based plants and then shipped to Seattle,
Washington, for distribution to world markets. By-
products of salmon canning have gained commercial
importance in Alaska in the past few years. The eggs of
all species are processed into caviar and fish bait and the
heads and viscera, which were formerly discarded, are
now frequently processed into pet food. The annual
value for these products has been several million dollars.

1<.

•vak

Figure 4. -Pink salmon spawning in the intertidal zone of a creek.

In addition to the commercial uses for pink salmon,
Indians and Eskimos along the Arctic coasts take thou-
sands of them in traps and gill nets for personal use.

RESEARCH AND MANAGEMENT

The pink salmon is an important source of high-quality
protein and is also a renewable resource— one that can be
maintained for future generations if properly used and
conserved. The Alaska Department of Fish and Game is
responsible for tliis use and conservation.

The foremost aim of the State agency is to get the
proper number of spawners into the streams to maintain
a high level of production. Management includes regu-
lation and enforcement of fishing seasons, areas, and gear.
The salmon fishing regulations, which are set during the
winter before the fishing season, are based on knowledge
of spawning escapements, abundance of young salmon
migrating seaward, and estimates of ocean mortality.

Research biologists ofseveral agencies assist the fishery
managers by determining the effects of different numbers
of parent spawners on the number of young produced,
the factors that cause mortaUties of eggs and fry in the
gravel, and the migration paths and mortalities in the
estuaries. The 2-year life cycle of pink salmon permits
relatively quick answers to studies of their fate at sea and
quick response to management. The Bureau of Commer-
cial Fisheries has several research stations in Alaska where
biologists study factors that affect pink salmon produc-
tion in fresh water, in intertidal areas, and along estuarine
and coastal migration routes. The headquarters for these
investigations is the Bureau of Commercial Fisheries
Biological Laboratory at Auke Bay near Juneau in south-
eastern Alaska. The United States Forest Service and the
Alaska Department of Fish and Game are studying the
effects of logging on pink salmon production. All ot these
research groups are working on the development of
techniques for improving and extending spawning grounds
for pink salmon.

Table 2. Numbers of fish, weight, numbers of 48-pound cases, and wholesale value of canned
pink salmon caught in Alaska, 1957-66. (Not including subsistence catches)

Wholesale value

Salmon

Standard

of canned

Year

caught'

Pounds^

cases^

products'*

Millions

Millions

Thousands

Millions

1957

54

714

$16.6

1958

--

121

1,548

32.1

1959

--

48

635

15.0

1960

--

53

731

16.8

1961

22

104

1,266

34.5

1962

44

143

1,893

44.6

1963

34

125

1,570

34.0

1964

45

162

1,928

29.0

1965

20

75

932

22.3

1966

40

177

2,042

55.1

Average

34

106

1,233

$28.0

'Source: for 1961-65-Alaska Dep. Fish Game, Statist. Leafl. 11, Table 10; for 1966-Unpub-

lished data. Bureau of Commercial Fisheries Statistical Office.

^Weight of whole or round fish. Source: Alaska Dep. Fish Game, Statist. Leafl. 1 1 , Table 21.
^A standard case contains 48 1 -pound cans.
"* Pacific Fisherman 1967 Yearbook, page 1 10.

PUBLICATIONS ON PINK SALMON

ALLEN, GEORGE H., and WILLIAM ARON.

1958. Food of salmonid fishes of the western
North Pacific Ocean. U.S. Fish Wildl. Serv.,
Spec. Sci. Rep. Fish. 237, iv + 1 1 pp.

BURNER, CLIFFORD J.

1964. Pacific salmon. U.S. Fish Wildl. Serv.,
Fish. Lean. 563, 11 pp.

DAVIDSON, FREDERICK A.

1934. The homing instinct and age at maturity
of the pink salmon {Oncorhvnchus gorbuscha).
Bull. U.S. Bur. Fish. 15: 27-39.

DAVIDSON, FREDERICK A., and O. EUGENE
SHOSTROM,

1936. Physical and chemical changes in the pink
salmon during the spawning migration. U.S.
Bur. Fisii., Invest. Rep. 33, ii + 37 pp.

HELLE, JOHN H., RICHARD S. WILLIAMSON, and

JACK E. BAILEY.

1964. Intertidal ecology and life history of pink
salmon at Olsen Creek, Prince William Sound,
Alaska. U.S. Fish Wildl. Serv., Spec. Sci. Rep.
Fish. 483, iv + 26 pp.

KASAHARA, HIROSHI.

1963. Salmon of the North Pacific Ocean. Part I,
Catch Statistics for North Pacific salmon. Int.
N. Pac. Fish. Comm., Bull. 12:7-82.

McNEIL, WILLIAM J.

1966. Effect of the spawning bed environment
on reproduction of pink and chum salmon.
U.S. Fish Wildl. Serv., Fish. Bull. 65: 495-523.

NEAVE, FERRIS.

1966. Pink salmon in British Columbia. Int. N.
Pac. Fish. Comm., Bull. 18: 71-79.

PARKER, ROBERT R.

1968. Marine mortality schedules of pink salmon
of the Bella Coola River, Central British Colum-
bia J. Fish. Res. Board Can. 25: 757-794.

ROUNSEFELL, GEORGE A.

1957. Fecundity of North American Salmonidae.
U.S. Fish Wildl. Serv., Fish. Bull. 57: 451-468.

SHERIDAN, WILLIAM L. (editor)

1966. Proceedings of the 1966 Northeast Pacific
Pink Salmon Workshop. Alaska Dep. Fish Game,
Inform. Leafl. 87, 168 pp.

Figure 5. -Hauling in the net on a pink salmon purse seiner. When set for fishing, the net encloses an area of about 2 acres.

WILIMOVSKY, N. J. (editor)

1962. Symposium on pink salmon. H. R. Mac-
Millan Lect. Fish., Univ. British Columbia,
Vancouver, 228 pp.

MS. ■^^1703

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DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

BUREAU OF COMMERCIAL FISHERIES

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