Coho Salmon

Physical Characteristics

Coho salmon are characterized by their silvery sides and dark blue-green backs when in marine environments. They have small black spots on their backs and on the upper lobe of their caudal (tail) fin. The mouth is dark grey to black along the gumline. During spawning, males develop a hooked snout (kype) and their bodies turn reddish to dark maroon. Females also change color but less dramatically. They have a streamlined, fusiform body shape.

Habitat & Distribution

Coho salmon are anadromous, meaning they hatch in freshwater streams, migrate to the ocean to feed and grow, and then return to freshwater to spawn. They prefer clear, cold streams and rivers with gravel bottoms for spawning. In the ocean, they inhabit coastal waters of the North Pacific. Their distribution spans from Hokkaido, Japan, and eastern Russia, across the Bering Sea, and along the west coast of North America from Alaska to Monterey Bay, California.

Size & Weight

Adult Coho salmon typically range from 45 to 70 centimeters (18-28 inches) in length and weigh between 2.5 to 7 kilograms (5.5-15 pounds). The maximum recorded size can reach up to 108 cm (42.5 inches) and over 15 kg (33 pounds).

Similar Looking Species

Coho salmon can be confused with other Pacific salmon species, particularly Chinook salmon ('king salmon'). Key distinguishing features for Coho include white gums with black along the gumline (Chinook have entirely dark gums), and spots primarily on the upper lobe of the caudal fin (Chinook often have spots on both lobes). Sockeye salmon are typically smaller, have no spots on their back or tail, and turn bright red during spawning. Pink salmon have large spots on their entire tail and back.

Ecological Role

Coho salmon play a crucial ecological role in both marine and freshwater ecosystems. As juveniles in freshwater, they feed on insects and small invertebrates, helping to regulate these populations. In the ocean, they are primarily piscivores, preying on smaller fish and squid, thus acting as important predators in the marine food web. Upon returning to freshwater to spawn, their carcasses provide significant nutrient input to stream ecosystems, supporting a wide range of invertebrates, other fish, birds, and riparian mammals. They are also a prey species for larger marine mammals, birds, and other fish. Conservation status varies by population; some populations are considered 'Threatened' or 'Endangered' under the Endangered Species Act in the US, while others are stable.

Identified on: 9/22/2025

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