Anadromous Fish : Coho Salmon
 
Coho salmon belong to the family Salmonidae and are one of eight species of Pacific salmonids in the genus Oncorhynchus. Coho salmon are anadromous (adults migrate from a marine environment into the fresh water streams and rivers of their birth) and semelparous (spawn only once and then die). Coho spend approximately the first half of their life cycle rearing in streams and small freshwater tributaries. The remainder of the life cycle is spent foraging in estuarine and marine waters of the Pacific Ocean prior to returning to their stream of origin to spawn and die. Most adults are three-year old fish, however, some precocious males known as "jacks" return as two-year old spawners. A returning adult may measure more than two feet in length and weigh an average of eight pounds.
The species was historically distributed throughout the North Pacific Ocean from central California to Point Hope, Alaska, through the Aleutian Islands, and from the Anadyr River, Russia, south to Hokkaido, Japan. Historically, this species probably inhabited most coastal streams in Washington, Oregon, and central and northern California. Some populations, now considered extinct, are believed to have migrated hundreds of miles inland to spawn in tributaries of the upper Columbia river in Washington, and the Snake river in Idaho.
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