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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