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Coho Salmon
Coho salmon, also known as "silver salmon," are anadramous fish. That means they are born in freshwater, migrate to saltwater, and return to freshwater to spawn. Adult anadramous coho range from 8-12 pounds. They are a bright silver color in the ocean, but turn red when spawning. Upper and lower jaws become "hooked" as coho approach spawning. Sharp teeth appear on tongue and roof of mouth. Spotting on tail fin is limited to the upper half. Coho have black mouths and white gums.
The eggs hatch in the late winter or early spring after 6 to 7 weeks in the redd. Once hatched, they remain mostly immobile in the redd as the alevin life-stage, which lasts for 1-2 weeks. The alevins no longer have the protective egg shell, or chorion, and rely on their yolk sac for nourishment during growth. The alevin life stage is very sensitive to aquatic and sediment contaminants. When the yolk sac is completely resorbed by the alevin it will swim up out of the redd.
Young coho spend one to two years in their freshwater natal streams,often spending the first winter in off-channel sloughs, before undergoing a transformation to the smolt life-stage. Smolts are generally 100-150mm and their parr marks are faded and the silver scales characteristic of the adult life-stage start to dominate. Smolts migrate to the ocean in late March through July. Some fish leave fresh water in the spring, spend summer in brackish estuarine ponds and then migrate back into fresh water in the fall. Coho salmon live in the salt water for one or two years before returning to spawn.
Some precocious males known as "jacks" return as two-year-old spawners. Spawning males develop a strongly hooked snout and large teeth.
Coho salmon are the backbone of the Alaska troll fishery, however, the majority are caught by the net fishery (Gillnet and Seine). Coho salmon average 3.5% by fish of the annual Alaska salmon harvest; 5.9% by weight of the annual Alaska salmon harvest.
This species is a game fish and provides fine sport in fresh and salt water from July to December, especially with light fishing tackle. It is one of the most popular sport fish in the Pacific Northwest of the United States. Its popularity is due in part to the reckless abandon which it frequently displays chasing bait and lure while in salt water, and the large number of coastal streams it ascends during its spawning runs. Its habit of schooling in relatively shallow water, and often near beaches, makes it accessible to anglers on the banks as well as in boats.
Young coho are voracious feeders focusing on plankton and aquatic insects in fresh water. Once they reach salt water they turn to a diet of fish. Adults returning to fresh water do not feed actively.
The traditional range of the coho salmon runs from both sides of the North Pacific ocean, from HokkaidÅ, Japan and eastern Russian, around the Bering Sea to mainland Alaska, and south all the way to Monterey Bay, California. Coho salmon have also been introduced in all the Great Lakes, as well as many other landlocked reservoirs throughout the United States.