Facts: What is a Salmon?

Basic Fish

Salmon are fish. That's pretty basic. But . . . what is a fish, exactly?


It's a cold-blooded, water dwelling vertebrate with gills, fins, and a body that is usually covered with scales. They breathe with gills, which are covered by opercula. They can sense their environment in a variety of ways. Along what is called the lateral line, fish have sensors that detect motion, vibration, and sound. Salmon also have an excellent sense of smell.

Did you know that the two comma-shaped holes on either side of a salmon's head are its noses? These olfactory receptors absorb molecules from water that convey information to the fish about its environment.

Most fish live in either salt water or fresh. But some fish are diadromous (dye-AD-ruh-mus) — they can live in fresh and salt water, at different times in their lives. Catadromous fish are born in salt water, move to fresh water to feed, and return to salt water to spawn (lay their eggs). Anadromous (ah-NAD-ruh-mus) fish begin their lives in fresh water, move to salt water to feed, and return to fresh water to spawn.

fish external anatomy

Salmon, and their relatives the steelhead, are anadromous fish. They begin their lives as eggs in the cold mountain streams, such as those of central Idaho. They grow to adults in the Pacific Ocean, and return to their birth streams to spawn.

Click here for info and a picture of the salmon life cycle!

Guess What?

Salmon are born in a bed of gravel chilled by cold water. Doesn't sound appealing to humans, but fish love it!

Did you know?

The "Kokanee" Sockeye are found only in Idaho lakes — they don't migrate but instead remain landlocked!

Interesting Salmon Facts!

Idaho's salmon must swim as far as 900 miles to reach their spawning sites! As salmon migrate, their bodies change. Males, for example, develop a hooked snout and a hump on their back. Female salmon dig nests in gravel at the river bottom, deposit their eggs, then spend their final days defending these nests, called redd.

Salmon depositing eggs in a redd

In the next section, you can explore the problems salmon face today. Look at the disturbances caused by humans, and other issues affecting salmon survival.

Thanks to Idaho Fish and Game and Project WILD for all of their help and information. All information in these sites from "Wild About Salmon" is copyrighted by the Idaho Department of Fish and Game and Idaho Project WILD, 1999. Written permission was granted to use this material for educational purposes.
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