coho salmon

coho salmon
Name	Coho salmon
Status	LC
Status system	IUCN3.1
Genus	Oncorhynchus
Species	kisutch
Authority	(Walbaum, 1792)

coho salmon is an anadromous fish species native to the North Pacific Ocean and its tributary rivers. It is a member of the genus Oncorhynchus, which includes other Pacific salmon like chinook salmon and sockeye salmon. The species is known for its importance in both commercial fisheries and Indigenous cultural practices, though many populations have faced significant declines.

Description and identification

Adult coho salmon in the ocean are characterized by bright silver sides and dark blue backs. Upon entering freshwater to spawn, males develop a pronounced kype, or hooked jaw, and their bodies turn a vivid red with darker greenish heads. Spawning females also change color but are generally less dramatically colored than males. They can be distinguished from other Oncorhynchus species by their white gums and the presence of small black spots on the upper lobe of the caudal fin. The average adult size ranges from 24 to 30 inches in length and weighs between 8 and 12 pounds, though individuals in specific systems like the Columbia River can grow larger.

Distribution and habitat

The native range of coho salmon extends from the coastal waters of Hokkaido and eastern Russia across the Bering Sea to Alaska, and south along the North American coast to Monterey Bay in California. Major populations are supported by river systems such as the Sacramento River, the Klamath River, and the Fraser River. They primarily inhabit coastal waters and estuaries during their marine phase, while freshwater rearing occurs in cool, clear streams with moderate gradient and abundant gravel substrates for spawning. Significant hatchery programs exist in regions like Puget Sound and the Great Lakes, where they were introduced.

Life cycle and reproduction

Coho salmon are semelparous, completing their entire life cycle in three years. Adults typically return to their natal streams in late fall or early winter. Females use their tails to create redds in gravel, where they deposit eggs that are then fertilized by males. After spawning, all adults die. The eggs incubate in the gravel over winter, and the alevin emerge in spring, absorbing their yolk sac before becoming free-swimming fry. Juveniles, or parr, often spend one full year in freshwater before migrating to the ocean as smolt. They then spend approximately 18 months feeding in the North Pacific before maturing and returning to freshwater to spawn.

Diet and predators

In the ocean, coho salmon are aggressive piscivores, feeding heavily on forage fish such as herring, sand lance, and smelt, as well as squid and crustaceans. In freshwater, juveniles consume aquatic and terrestrial insects, zooplankton, and smaller fish. Key marine predators include Pacific halibut, sharks like the salmon shark, pinnipeds such as Steller sea lions, and orcas. In freshwater and estuarine environments, they are preyed upon by river otters, belted kingfishers, great blue herons, and larger fish including northern pikeminnow.

Conservation status and threats

Globally, the species is classified as Least Concern by the International Union for Conservation of Nature, but numerous distinct population segments, particularly in the continental United States, are listed as Threatened or Endangered under the Endangered Species Act. Major threats include habitat degradation from logging, agriculture, and urbanization; barriers to migration like dams on the Snake River; historical overfishing; and negative interactions with hatchery fish. Climate change impacts, such as increased water temperatures and altered stream flows, pose significant long-term risks.

Relationship to humans

Coho salmon have been a vital resource for millennia, central to the subsistence, economy, and culture of peoples like the Tlingit, Haida, and Coast Salish. Commercially, they are harvested in major fisheries in Alaska, British Columbia, and the Pacific Northwest, often caught using gillnets and trolling. They are also a highly prized sport fish, supporting significant recreational industries. Large-scale hatchery production, managed by agencies like the Washington Department of Fish and Wildlife, aims to supplement wild stocks and support harvests, though not without ecological controversy.

Category:Oncorhynchus Category:Fish of the Pacific Ocean Category:Commercial fish