FWS Focus

Overview

Characteristics
Overview

Coho salmon are a species of Pacific salmon which inhabit the Pacific coast in California, Oregon, Washington, British Columbia, and Alaska.  These fish are also known as silver salmon.  The average size adult coho is around 24 inches and 8-9 pounds, but can range up to 20lbs. ?Coho salmon have dark metallic blue or greenish backs with silver sides and a light belly and there are small black spots on the back and upper lobe of the tail while in the ocean.  

The species was historically distributed throughout the North Pacific from central California to Point Hope, Alaska, through the Aleutian Islands, and from the Kamchatka Peninsula in Russia, south to Japan. Coho inhabit most coastal streams in Washington, Oregon, and central and northern California. Some populations are believed to have migrated hundreds of miles inland to spawn in tributaries of the upper Columbia River in Washington, and the Snake River in Idaho. Coho exist throughout Alaska wherever they have access to both freshwater habitat and the Pacific Ocean. 

Scientific Name

Oncorhynchus kisutch
Common Name
coho salmon
silver salmon
FWS Category
Fishes
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Habitat

Characteristics
Habitat

Coho salmon often inhabit smaller rivers and tributaries along the Pacific coast.  They can reside in rivers and streams that are too small for other species, such as Chinook salmon.  As adults, coho salmon often forage in shallow coastal waters but can also migrate thousands of miles in the North Pacific Ocean before returning to their natal streams.  Spawning habitat is small streams with stable gravel substrates with cool, consistent water flow.  

River or Stream
Coastal
Characteristic category

Food

Characteristics
Food

Young coho salmon which inhabit lakes and rivers eat mainly insects. When migrating to the sea, the young salmon dine on plankton and small crustaceans. As they grow and move further out to sea, they begin to eat larger forage such as anchovies, sand lance, herring and squid. 

Characteristic category

Behavior

Characteristics
Behavior

Migration Behavior 

Coho salmon begin life in freshwater tributaries all along the Pacific coast.  Coho spend approximately the first half of their life cycle (18 months) rearing and feeding in streams and small freshwater tributaries.  The juveniles migrate to the ocean in the spring. The remainder of the life cycle (another 18 months) is spent foraging in estuarine and marine waters of the Pacific Ocean. ?The adults return to spawn in the river where they were born, usually in the fall (September to December). Spawning habitat is small streams with stable gravel substrates and cool water temperatures.  Like all Pacific salmon, coho spawn only once and then die. 

Characteristic category

Physical Characteristics

Characteristics
Size & Shape

Coho salmon average 24 inches long, but some adults have been recorded as long as 42.5 inches.

Weight

On average, coho salmon weigh between seven and 11 pounds, but can reach up to 36 pounds. 

Characteristic category

Life Cycle

Characteristics
Reproduction

Coho salmon return to their natal streams in the fall, usually after the much larger Chinook salmon have entered their natal rivers.  In general, adult coho salmon migrate from the sea, gather at the river mouths, and proceed upstream when autumn rains signi?cantly increase water ?ows. Upon arriving at spawning areas, the female will dig a nest, called a redd, with her tail.  Upon completing the redd, the female drops her eggs, and the male will fertilize the eggs.  The female will then cover the eggs with gravel.  The eggs will remain in the streambed over the winter.  The young salmon hatch in the early spring, and emerge from the gravel to begin feeding in the stream.   

Life Cycle

After they hatch, young coho spend the next year in freshwater before undergoing changes necessary to survive in saltwater.  This process is called ‘smoltification’.  Once the young coho are ready, they migrate out of freshwater and into the ocean.  They will spend the next 18 months feeding, growing and becoming adults.  As adults, they will return to the same river where they were born three years earlier. 

Geography

Characteristics
Range

Coho salmon are widely distributed in the North Paci?c Ocean.  They range from the Kamchatka Peninsula in Russia, southward towards Hokkaido, Japan. In North America, coho range from Point Hope in Alaska, southward to Chamalu Bay in Baja California and all the way into Mexico.   

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