The upriver salmon migration is one of
nature’s most exciting dramas. But to the
seven species of Pacific salmon (chinook,
chum, coho, pink and sockeye salmon, as
well as sea-run cutthroat and steelhead
trout), it is a long, strenuous and desperate
race against time, with every obstacle
taking its toll.

Pacific salmon belong to a group called
anadromous fish that includes Atlantic
salmon, sturgeon, lampreys, shad and
herring. Anadromous fish hatch and live the
first part of their lives in fresh water, then
migrate to the ocean to spend their adult
lives, which may be as short as 6 months or
as long as 7 years. When they reach sexual
maturity, they return to the freshwater
stream of their origin to lay their eggs.
Although Atlantic salmon may repeat this
cycle several times, Pacific salmon make
the round trip only once.

Migration between fresh and salt water
occurs during every season of the year,
depending on the latitude and genetic
characteristics of the fish. Groups of fish
that migrate together are called runs or
stocks, Salmon spawn in virtually all types
of freshwater habitat, from intertidal areas
to high mountain streams. Pacific salmon
may swim thousands of miles to get back to
the stream where they hatched.

However, only a small percentage of salmon
live to reach their natal stream or spawning
ground, Those males that survive the trip
are often gaunt, with grotesquely humped
backs, hooked jaws and battle-torn fins. The
females are swollen with a pound or more of
eggs. Both have large white patches of
bruised skin on their backs and sides.

Since salmon do not feed after they leave
the ocean, some die on the way to spawn
because they lack enough stored body fat to
make the trip. Many become caught in
fishermen’s nets. Those that evade the nets
may have to swim through polluted waters
near cities. Many make their way over
power dams, leaping up from one tiny pool
to the next along cement stairstep cascades
called fish ladders. In the tributary
streams, waterfalls and rapids are steep
and swift enough to eliminate all but the
strongest salmon. Otters, eagles and bears

Pacific Salmon
Oncorhynchus spp.

stalk the salmon in shallow riffles. Once on
the spawning grounds, the fish battle each
other: females against females for places to
nest, males against males for available
females.

The female builds her nest, called a redd,
by agitating the bottom gravel with her
fins and tail and bending her body into a

U shape first one way, then the other.

As soon as she has excavated a depression,
she settles into it and deposits her first
batch of eggs, or roe. The male then moves
alongside and deposits his sperm, called
malt, over the roe. The female rakes her tail
back and forth to cover the redd with loose
gravel. She then excavates her next redd a
short distance upstream.

The process continues until all the roe and
milt have been deposited. One pair of
salmon may have as many as seven redds,
though four or five is average. The salmon
die within a few days of spawning.

The translucent salmon eggs range in color
from pale yellowish-orange to dark reddish-
orange. The color varies both by species
and within species and is determined by
water temperature, sediment composition,
age and other factors. The eggs vary in size

from the tiny sockeye roe (about 1/4 inch) to
the large chum roe (almost 1/2 inch).

Incubation time ranges from 5 to 10 weeks.
The newly hatched fish are called fry, or sac
fry because they continue to feed on the
yolk sac attached to their bellies. Depending
on water temperature, species and other
factors, they may stay in the gravel for
several weeks before swimming up into

the open water of the stream, where they
feed on plankton and other tiny aquatic
organisms. By the time they reach fingerling
size (about 3 inches), most pink and chum
salmon have begun the long journey
downstream and out to sea. Sockeye, coho
and most chinook spend from 1 to 2 years in
fresh water before heading out to sea.

As the stream current carries the young
salmon to the ocean, where they will
spend the majority of their lives, their
bodies undergo smoltation, physical and
chemical changes that enable them to
survive in salt water.

Most adult Pacific salmon species feed on
aquatic insects and small fish. However,
sockeye are filter feeders. They take in
water full of plankton, and as the water
flows back out of their mouths, specialized

When salmon return to their home
spawning grounds, the female selects a
place to nest and digs a depression (called
aredd) in the streambed gravel. She then
deposits her first batch of eggs (roe) and the
male moves in to fertilize them, spreading a
cloud of sperm (milt) over the roe.



organs called gilt rakers act like stralners,
holding the plankton in to be swallowed.

Some species of Pacific salmon stay within
a few hundred miles of their home river,
while others disperse north, south, west, or
in the case of salmon originating in Russian
and Japanese rivers and streams, east into
feeding grounds in the Aleutian islands and
other areas of the north Pacific. Chinook
salmon may travel as far as 2,500 miles
from their home stream and stay out at sea
4 to 7 years, Pink salmon, on the other
hand, seldom range more than 150 miles
from the mouth of their home river or
stream where they hatch in the fall, and
turn homeward in the spring, sometimes
traveling 45 miles per day to reach their
spawning grounds.

Pacific salmon encounter increasing human-
caused hazards in their migrations to and
from spawning grounds. All salmonids
require pure, well-oxygenated cold water

and are one or the first species to sufler
when water quality is degraded, Many
salmon stocks are seriously threatened by
habitat destruction, hydroelectric dams on
migratory rivers, harvest of rare stocks
and competition with hatchery fish. Some
stocks are so severely reduced that they
have been listed as endangered or
threatened species under the Endangered
Species Act. Endangered means they are
likely to become extinct. Threatened means
they are likely to become endangered in
the near future.

The winter-run of chinook salmon
originating in California’s Sacramento
River was listed as threatened in 1990 but
was reclassified to endangered in 1994. In
1992, the Snake River stock of sockeye
salmon was listed as endangered wherever
found. The spring-summer and fall runs of
chinook originating in Idaho's Snake River
were listed as threatened in 1992, but are
currently being considered for endangered

status. Uthers being considered [or listing:
include the Columbia River (Washington)
chinook. Coho salmon in southern Oregon
and along the northern and central
California coasts were recently designated
as threatened.

A 1991 report by the American Fisheries
Society indicated that 214 of about 400
stocks of salmon, steelhead and sea-run
trout in the Northwest and California are
at risk of extinction. The report also
indicated that 106 are nearly extinct.
Steelhead on the central California coast
and in the upper and lower Columbia River
areas are among populations recently listed
as threatened species.

Primary listing and recovery
responsibilities for Pacific salmon belong to
the Department of Commerce's National
Marine Fisheries Service. The U.S. Fish &
Wildlife Service and other federal and state
agencies also have recovery responsibilities.

Pacific salmon may swim hundreds of
miles to get back to the stream where they
hatched to spawn. The many obstacles the
salmon face on this journey are often
evident by bruised skin and torn fins.

Chinook
(Oncorhynchus tshawytscha)

The largest of the Pacific salmon, chinook
average about 24 pounds when they return
to their natal river to spawn, most after 2 or
3 years at sea. The chinook is the least
abundant of the Pacific salmon.

Chum salmon
(Oncorhynchus keta)

Chum make up about 13 percent of the West
Coast catch. They follow Pacific migration
paths and reach a common weight of about
12 pounds before returning to their natal
river to spawn.

Coho salmon
(Oncorhynchus kisutch)

Fourth in Pacific fishery abundance, coho
salmon is the number one sport fish. It
spends only one winter at sea, returning
the newt fall to spawn. It averages about
10 pounds when full grown.

Pink salmon
(Oncorhynchus gorbuscha)

The smallest of the Pacific salmon, pink
salmon average only about 3 to 5 pounds.
However, they make up more than half the
total West Coast commercial catch. Pink
salmon seldom travel more than 150 miles

from the mouth of their natal river.

Sockeye salmon
(Oncorhynchus nerka)

Sockeye salmon make up about 25 percent
of the West Coast salmon catch.
chum, they follow Pacific migration paths
and reach a weight of about 12 pounds
before returning to their natal river to
spawn.

US. Fish & Wildlife Service
http:/Awww.fws.gov
May 1998