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Coho salmon
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The Coho salmon, Oncorhynchus kisutch, (from the Russian ????? kizhuch) is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers".
ng their ocean phase, Coho have silver sides and dark blue backs. During their spawning phase, the jaws and teeth of the coho become hooked, and they develop bright red sides, bluish green heads and backs, dark bellies with dark spots on their back.
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Encyclopedia
The Coho salmon, Oncorhynchus kisutch, (from the Russian ????? kizhuch) is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers".
Description
During their ocean phase, Coho have silver sides and dark blue backs. During their spawning phase, the jaws and teeth of the coho become hooked, and they develop bright red sides, bluish green heads and backs, dark bellies with dark spots on their back. Sexually maturing coho develop a light pink or rose shading along the belly and the males may show a slight arching of the back. Mature coho salmon have a pronounced red skin color with darker backs and average 28 inches in length and seven to 11 pounds in weight, although coho weighing up to 36 pounds have been reported. Mature females may be darker than males, with both showing a pronounced hook on the nose.
Reproduction
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.
Range
The traditional range of the coho salmon runs from both sides of the North Pacific ocean, from Hokkaido, 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.
Human Uses
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. (Alaska Seafood Marketing Institute, 2003, p.2)
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.
Ocean caught coho is regarded as excellent table fare. It has a moderate to high amount of fat, which is considered essential when judging taste. Only Spring Chinook and Sockeye salmon have higher levels of fats in their meat.
Historically, the coho, along with other species, has been a staple in the diet of several Indigenous Peoples, who would also use it to trade with other tribes farther inland. The coho salmon is also a symbol of several tribes, representing life and sustenance.
Ecology
In their freshwater stages, coho feed on plankton and insects, and switch to a diet of small fishes as adults in the ocean. Spawning habitat is small streams with stable gravel substrates.
Salmonid species on the west coast of the United States have experienced dramatic declines in abundance during the past several decades as a result of human-induced and natural factors.
Conservation
The U.S. National Marine Fisheries Service has identified seven populations, called Evolutionary Significant Units (ESUs), of coho salmon in Washington, Oregon and California. Three of these ESUs are listed under the U.S. Endangered Species Act (ESA). These are the Lower Columbia River (threatened), Southern Oregon and Northern California Coasts (threatened), and Central Califorina Coast (endangered). The long-term trend for the listed populations is still downward, though there was one recent good year with an increasing trend in 2001.
On May 6, 1997, the National Marine Fisheries Service, on behalf of the Secretary of Commerce, listed as threatened the Southern Oregon/Northern California Coast coho salmon ESU. 62 Fed.Reg. 24588. The coho salmon population in the Southern Oregon/Northern California region has declined from an estimated 150,000 – 400,000 naturally spawning fish in the 1940s to fewer than 10,000 naturally producing adults today. The dramatic reduction in the coho salmon population has been due to many natural and man-made conditions, including long-term trends in atmospheric conditions, such as El Niño, which causes extremes in annual rainfall on the northern California coast; the predation of coho salmon by the California Sea Lion and Pacific Harbor Seal; and commercial timber harvesting.
The Puget Sound/Strait of Georgia population in Washington state is a U.S. National Marine Fisheries Service "Species of Concern". Species of Concern are those species about which the U.S. National Oceanic and Atmospheric Administration has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the ESA.
Many groups are actively involved in conservation of the coho salmon and their habitat. The Salmon Protection and Watershed Network (SPAWN) has achieved great success over the last 10 years protecting the coho salmon population in the San Geronimo Creek and Lagunitas Creek Watersheds of West Marin, California, with a combination of grassroots activism, habitat restoration, policy development and biological monitoring. The coho salmon in the San Geronimo Creek and Lagunitas Creek Watersheds are the southernmost, stable population of wild coho in California and account for almost 30% of the state's coho in <1% of the state's designated coho habitat.
Technical Reports
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