Silver in the ocean, coho undergo an amazing spawning transformation. Males get bright red flanks, dark green backs, and dark gray bellies and heads; females sport a paler version of the same colors. Males' jaws become grotesquely hooked. The guns are white–very noticeable when the fish are in their dark spawning colors.
Most coho spend 1 ½ years at sea, although about 10 percent of males, called "jacks," stay only 6 months. They are not long-distance migrants; Columbia River coho range only from northern California to Vancouver Island, and stay close to shore. Coho migrate upriver in late summer and fall and spawn from October through December.
Coho fry stay in fresh water for 18 months before heading out to sea. Unlike other salmon fry, young coho are colorful, with orange bellies and black-and-white bordered fins. Their colors aid them in territorial displays; they are the most aggressive of all salmon fry, both to their own and other species.
Unlike chinook, coho will spawn in small coastal streams that have been less affected by development. However, wild coho in the Columbia Basin have been hard hit by loss of stream habitat, and continue to decline. Ninety percent of Columbia River coho are now hatchery-raised.
