Know Your Fish- Salmon, Trout,
Steelhead
A Salmon's Life
Cycle
The fish known to us as salmon are native to the North
Pacific on the North American and Asian coasts. They are also
known to a far lesser extent in the North Atlantic on both the
North American and European coasts. This family is
characterized by their flashing silver color and their
fighting heart.
The Pacific salmon consists of a large
number of game fish including trout, steelhead, and the five
salmon most familiar to Pacific Northwest fisherman. They
belong to the genus Oncorhynchus, meaning "hooked nose". The
name is from the Greek words onkos, meaning "hook", and
rhynchos, meaning "nose". When you see their pictures you can
see that they are well named. The popular and scientific names
for the fish are: chinook (Oncorhynchus tshawytscha), coho
(Oncorhynchus kisutch), sockeye (Oncorhynchus nerka), pink
(Oncorhynchus gorbuscha), chum (Oncorhynchus keta), and
steelhead (Oncorhynchus mykiss).
Fish that spend their
lives in both marine and freshwater systems (diadromous
animals) exhibit some of the most spectacular migratory
behavior. Anadromous fish (those that spend most of their
lives in the ocean but migrate to fresh water to spawn) such
as Pacific salmon also have unique migratory
patterns.
Salmon are born in the gravel beds of streams
and rivers, anywhere from a few yards to hundreds of miles
from the ocean, where the eggs are generally laid in the fall
and winter and incubate for several months. The newly hatched
fish (alevin) emerge from spawned eggs and develop into young
fry. After feeding and growing for up to a year the fry move
down the streams and rivers toward the ocean. Juveniles (parr)
grow into larger fish (smolt) that convene near the
ocean.
Once in the ocean they spend a variable amount
of time, up to five years, feeding and growing. Sockeye, pinks
and chums will feed primarily on plankton and crustaceans such
as tiny shrimp, while chinook, coho, and steelhead eat smaller
fish. This is what makes them vulnerable to commercial and
sports fishermen using bait such as herring.
When the
adult fish are ready to spawn, they return to the river in
which they were born (natal river), using a variety of
environmental cues, including their lateral lines and the
Earth's magnetic field, the Sun, and water chemistry detected
through their incredible sense of smell. The fish stop feeding
as soon as they reenter their natal river and begin living on
their stored body fats.
Sockeye and chinook are the
toughest members of the family, traveling as far as 1000 miles
upstream to spawn. Chums, coho, and pinks usually spawn closer
to the ocean. They fight for weeks and months against all
forms of obstacles until, bruised and battered, they finally
reach the very spot in the stream or river where they were
born. The female then hollows out a nest (redd) in the gravel
up to a foot deep in a spot where the water will provide an
ample supply of oxygen for the eggs. When the nest is ready,
she lays up to 12,000 eggs and the male covers them with a
milky substance (milt) to fertilize them.
Once the
adult salmon have spawned, their life cycle has been completed
and they die. Nothing is wasted, their bodies are recycled by
nature to provide nourishment for other animals. Steelhead, on
the other hand, may migrate back to the ocean and spawn again
and because of this, they are not a true member of the Pacific
salmon.
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