Coho salmon are dark metallic blue to black on top with bright silver sides. They have black spots across the top of their body and on the top of their tail fin, but not on the bottom, which distinguishes them from chinook salmon. The gums of the lower jaw are gray or white. They are excellent swimmers and have muscular bodies that are both long and thick.
Before entering the ocean, young coho salmon feed on aquatic insects, zooplankton, and small fish. As adults in the ocean, coho salmon use their sharp teeth to feed on other fishes, squid, and crustaceans. The large amounts of euphasid shrimp they eat account for the deep, purplish red of their flesh.
In the Great Lakes, they eat alewives, lake chubs, rainbow smelt, and herring.
The native range for coho salmon is from California to Japan and, because they are so adaptable, they have been successfully introduced in the Great Lakes region and many lakes in Canada.
Coho salmon spend part of their life in the ocean and part in small, coastal freshwater streams. They choose streams with a weaker current than other salmon, such as chinooks. Young coho salmon also require adequate streamside cover to hide underneath, such as submerged branches and undercut banks. Some coho salmon spend their entire life in lakes, particularly those transplanted in the Great Lakes region.
- The hook that male coho salmon develop in their jaw during spawning is used to fight off other males for breeding privileges.
- The largest coho salmon ever caught was 31 pounds in 1947.
- Some Great Lakes fishermen locate coho salmon by watching for seagulls attacking herring in the water. Herring travel along the surface in large, tightly bunched groups.