Silver salmon or coho (Onchorhynchus kisutch), are a medium-size salmon, one of five Pacific species that have evolved over roughly the past 50 million years from the coast of California north to the Kuskokwim basin and Point Hope in Alaska. They also range from Hokkaido in Japan north to the Anadyr River in Kamchatka. They are anadromous fish, spawning in fresh water, hatching from eggs spawned into the gravel, rearing for one year in the river, then in spring smolting and running to the sea for two years and returning to spawn and die as adults. Their Homeric lifecycle brings nutrients from the sea to the land, as five anadromous salmonid species return to Alaskan rivers in summer and fall to spawn and recharge a vast ecosystem with lifegiving death.

Silvers prefer short coastal streams and are especially abundant on Kodiak Island, the North Gulf Coast, and southeast Alaska, where there are more than 2,000 rivers with spawning runs. The Kuskokwim drainage has the largest runs of silvers, with as many as one million running to spawn in peak years.

Silvers are preferred by fly fishers because they take the fly hard, and they are aggressive toward drys (especially pink deer-hair Pollywogs) skated across the fish's holding lies. They fight and jump like rainbows, to which they are closely related. Their upstream spawning migrations can run from mid-July through October in Alaska, and they provide that last bittersweet touch of seasonal fishing drama for the fly fisher.

Historically, the largest silvers (up to 30 pounds) came from southeast Alaska and British Columbia rivers, but since introductions of the species to the Great Lakes in the 1950s (to help control rampant alewife populations) larger specimens have been taken there. The current IGFA world record is a 33-pound Lake Erie kahuna taken on the Salmon River at Pulaski, New York.

In the rivers near Cordova, Alaska, including the mighty Copper River drainage, silvers continue to thrive because their habitats have not been destroyed and they are not overharvested at sea or in the rivers. Unfortunately, that is not the case in the Northwest and British Columbia. Eighteen Columbia River silver populations have been listed by U.S. fisheries scientists as extinct due to dam building, habitat destruction, and overfishing. And 34 silver populations from northern California to the state of Washington are at risk. In the past decade, British Columbia's Skeena River silver populations have collapsed. Their recovery is doubtful.