Coho salmon

This article is about the species of salmon. For the Black Ball car ferry, see MV Coho.

Coho Salmon
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Superclass:	Gnathostomata
Class:	Actinopterygii
Subclass:	Neopterygii
Order:	Salmoniformes
Family:	Salmonidae
Genus:	Oncorhynchus
Species:	O. kisutch
Binomial name
Oncorhynchus kisutch (Walbaum, 1792)

The Coho salmon, Oncorhynchus kisutch, (from the Russian кижуч kizhuch) is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". It is the state animal of Chiba, Japan.

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. They develop bright red sides, bluish green heads and backs, dark bellies and dark spots on their backs after they go in to fresh water. 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 adults have a pronounced red skin color with darker backs and average 28 inches (71 cm) and 7 to 11 pounds (3.2 to 5.0 kg) occasionally reaching 36 pounds (16 kg). Mature females may be darker than males, with both showing a pronounced hook on the nose.^[1]

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 6–7 weeks. Alevin 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 sedimental contaminants. When the yolk sac is completely resorbed, the alevin leaves the redd. Young coho spend one to two years in their freshwater natal streams,often spending the first winter in off-channel sloughs, before transforming to the smolt life-stage. Smolts are generally 100–150 millimetres (3.9–5.9 in) and their parr marks are faded and the adult's characteristic silver scales start to dominate. Smolts migrate to the ocean from late March through July. Some fish leave fresh water in the spring, spend summer in brackish estuarine ponds and then return to fresh water in the fall. Coho salmon live in salt water for one to three 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.

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  Male ocean phase Coho

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  Male freshwater phase Coho

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  Freshly caught coho

Range

Silver Salmon caught in the ocean just off Raspberry Island, Alaska in the Kodiak Archipelago.

The traditional range of the coho salmon runs from both sides of the North Pacific ocean, from Hokkaidō, Japan and eastern Russian, around the Bering Sea to mainland Alaska, and south all the way to Monterey Bay, California.^[2] Coho salmon have also been introduced in all the Great Lakes, as well as many 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.

During November 1997, a Portland television station and The Oregonian teamed with the Oregon chapter of the American Meteorological Society (AMS) to name the strong Columbia River Gorge winds through a contest. Some 7,000 entries were submitted to the "Name our East Wind Contest" with a total of 2,424 different names. The name 'Coho' was judged to be the best name, since it is easy to pronounce (and spell), it's an indigenous name to the Pacific Northwest, Coho salmon are wild fast swimmers analogous to the wind, and it relates to the widely known westerly Chinook winds that are also a name of a salmon.

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.^[3]

Conservation

The U.S. National Marine Fisheries Service (NMFS) has identified seven populations, called Evolutionary Significant Units (ESUs), of coho salmon in Washington, Oregon and California.^[4][5] Four of these ESUs are listed under the U.S. Endangered Species Act (ESA).^[6] These are the Lower Columbia River (threatened), Oregon Coast (threatened), Southern Oregon and Northern California Coasts (threatened), and Central California 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.^[7]

The Puget Sound/Strait of Georgia ESU in Washington state is a NMFS "Species of Concern".^[8] Species of Concern are those species for which insufficient information prevents resolving the U.S. National Oceanic and Atmospheric Administration's concerns regarding status and threats and whether to list the species under the ESA.

On May 6, 1997, NMFS, on behalf of the Secretary of Commerce, listed as threatened the Southern Oregon/Northern California Coast coho salmon ESU.^[9] 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. These reductions are due to natural and man-made changes, including short-term atmospheric trends, such as El Niño, which causes extremes in annual rainfall on the northern California coast; predation by the California Sea Lion and Pacific Harbor Seal; and commercial timber harvesting.^{[citation needed]}

More than 680,000 coho returned to Oregon in 2009, double that of 2007. The Oregon Department of Fish & Wildlife required volunteers to herd fish into hatchery pens. There were reports of creeks with so many fish that "you could literally walk across on the backs of Coho," said Grant McOmie, outdoors correspondent for a Portland television station. Lower temperatures in 2008 North Pacific waters brought in fatter plankton which, along with greater outflows of Columbia River water, feeding the resurgent populations. The 2009 run was so large that food banks were able to freeze 40 tonnes (39 long tons; 44 short tons) for later use.^[10]

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Footnotes

1. ^ http://www.nmfs.noaa.gov/pr/species/fish/cohosalmon.htm
2. ^ Peter B. Adams et al (2007-09). "Coho Salmon Are Native South of San Francisco Bay: A Reexamination of North American Coho Salmon's Southern Range Limit". Fisheries 32 (9): 441–451. doi:10.1577/1548-8446(2007)32[441:CSANSO]2.0.CO;2. ISSN 1548-8446. http://afsjournals.org/doi/abs/10.1577/1548-8446(2007)32%5B441:CSANSO%5D2.0.CO%3B2. Retrieved 2011-01-30. 
3. ^ "Pacific salmonids threats". U.S. National Marine Fisheries Service. http://www.nmfs.noaa.gov/pr/species/fish/salmon.htm. 
4. ^ "Evolutionary Significant Units". U.S. National Marine Fisheries Service. http://www.nmfs.noaa.gov/pr/glossary.htm#esu. 
5. ^ "Coho salmon ESUs". http://www.nwr.noaa.gov/ESA-Salmon-Listings/Salmon-Populations/Coho/. 
6. ^ "Endangered Species Act". http://www.nmfs.noaa.gov/pr/laws/esa/. 
7. ^ "2005 status review report". http://www.nwr.noaa.gov/Publications/Biological-Status-Reviews/upload/SR2005-allspecies.pdf. 
8. ^ "Species of Concern". http://www.nmfs.noaa.gov/pr/species/concern/. 
9. ^ 62 Fed.Reg. 24588
10. ^ Millman, Joel (January 21, 2010). "Fish Boom Makes Splash in Oregon". Wall Street Journal. http://online.wsj.com/article/SB10001424052748703657604575005562712284770.html. Retrieved January 21, 2010. 

References

• "Oncorhynchus kisutch". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=161977. Retrieved 24 January 2006. 
• Froese, Rainer, and Daniel Pauly, eds. (2005). "Oncorhynchus kisutch" in FishBase. 10 2005 version.
• "Coho salmon in the Great Lakes". http://www.seagrant.wisc.edu/greatlakesfish/cohosalmon.html. 

Technical reports

• Use of three microhabitats by juvenile coho salmon in Jordan Creek during the winter, 2004-2005 / by Ryan J. Briscoe. Hosted by the Alaska State Publications Program.

External links