Fish
Coho Salmon
Oncorhynchus kisutch · also called coho salmons, silver salmon
A coho salmon returning to spawn barely resembles the bright silver fish that left the same stream years earlier, its body now deep red, its jaw curved into a hooked kype built for fighting rival males over a single, final chance to breed.
Overview
The coho salmon, Oncorhynchus kisutch, is a Pacific salmon native to coastal ocean waters and freshwater rivers and streams across the North Pacific, from California north through Alaska and into eastern Russia and Japan. Its unusually long freshwater juvenile stage, dramatic spawning transformation, and importance to commercial and sport fisheries make it one of the more ecologically and economically significant Pacific salmon species.
A slower start than most salmon
While many Pacific salmon rush to the ocean within months of hatching, the coho salmon takes its time, spending roughly a year and a half growing in fresh water before it ever sees the sea.
Status
Near Threatened — declining significantly in parts of its range, particularly California and the Pacific Northwest, due to dams, habitat degradation, and water diversion.
Coho Salmon: common questions
Why does the coho salmon spend so long in fresh water compared to other salmon?
A coho salmon typically spends about 18 months in fresh water as a juvenile before migrating to the ocean, a considerably longer freshwater residency than several other Pacific salmon species, which often head to sea within just a few months of hatching.
Why is the coho salmon also called silver salmon?
In the ocean, this species has a bright silver body, which is where the alternate name silver salmon comes from, though its colouration transforms into a deep red to maroon shade once it returns to fresh water to spawn.
What is a kype and why does a coho salmon develop one?
A kype is a pronounced hooked jaw that a male coho salmon develops during the spawning season, along with enlarged teeth, both used in physical competition with rival males over access to spawning females.
Why has the coho salmon declined in parts of its range?
Populations have declined significantly in areas such as California and the Pacific Northwest due to dam construction, habitat degradation, and water diversion, all of which interfere with the freshwater rivers and streams the species depends on for spawning and its unusually long juvenile stage.