Coho Salmon

• It returns to the exact stream where it hatched by smell: as a fry it memorises the chemical signature of its river and recognises it years later after thousands of kilometres in the open sea.
• It is semelparous: it spawns once and then dies, and its carcasses bring riverside forests an enormous quantity of nitrogen and phosphorus of oceanic origin.
• Its populations have disappeared from much of California because of dams and the degradation of the rivers.
• Unlike other Pacific salmon, the juveniles spend one or two full years in the stream before going down to the sea, which makes them far more dependent on freshwater quality.
• That freshwater phase is also its weak point: logging, dams and the loss of winter refuges in the streams are the main causes of its decline.
• It is semelparous: it breeds once and dies. The carcasses deliver marine nutrients to the riverside forest, a flow that sustains everything from the bears to the trees themselves.
• Before spawning the male develops a hooked jaw and the body turns deep red with a green head and back.
• Several populations on the west coast of the United States are protected under the Endangered Species Act, with evolutionarily significant units assessed separately.

Skeleton type

Vertebrate - internal bony skeleton (fish)

Habitat & environment

North Pacific Ocean and coastal rivers of North America and eastern Asia

Sexual maturity

3 years

Sources consulted: Lista Roja de la UICN; NOAA Fisheries; FishBase; Quinn, The Behavior and Ecology of Pacific Salmon and Trout

Best time: Autumn, during the spawning run upriver