A member of the Salmonidae family, the coho salmon is an extremely adaptable fish that occurs in nearly all of the same waters as does the larger chinook salmon, but it is a more spectacular fighter and the most acrobatic of the Pacific salmon.
By nature an anadromous species, the coho can adapt to an entirely freshwater existence and has done so with remarkable success in the Great Lakes of North America.
Identification. The body of the coho salmon is elongate and somewhat compressed, and the head is conical. For most of its life (in saltwater or lake, as well as newly arrived in a spawning river), this species is a dark metallic blue or blue green above, becoming silvery on the sides and the belly. There are small black spots on the back and on the upper lobe of the caudal fin. It can be distinguished from a chinook salmon by its lack of black spots on the lower lobe of the tail, and the white or gray gums at the base of the teeth; the chinook has small black spots on both caudal lobes of the tail, and it has black gums.
Spawning adults of both sexes have dark backs and heads, and maroon to reddish sides. The male turns dusky green above and on its head, bright red on its sides, and blackish below. The female turns a pinkish red on its sides. The male develops a prominent doubled-hooked snout, called a kype, with large teeth, which make closing the mouth impossible.
Size. Coho do not attain the size of their larger chinook brethren and in most places are caught around the 4- to 8-pound mark. The all-tackle world record is a Great Lakes fish of 33 pounds, 4 ounces, caught in the Salmon River, New York, in 1989. Fish to 31 pounds have been caught in Alaska, where the average catch is 8 to 12 pounds and 24 to 30 inches long.
silver salmon, silversides, hookbill, hooknose, sea trout, blueback; French: saumon coho; Japanese: gin-zake.
Distribution. The coho salmon is endemic to the northern Pacific Ocean and the rivers flowing into it, from northern Japan to the Anadyr River, Russia, and from Point Hope, Alaska, on the Chukchi Sea south to Monterey Bay, California. It has been infrequently reported at sea as far south as Baja California, Mexico. Most sea-run coho are encountered along the coasts and in spawning rivers.
The coho has been transplanted into the Great Lakes and into freshwater lakes in Alaska and along the U.S. Pacific coast, as well as into the states of Maine, Maryland, and Louisiana and the province of Alberta, Canada. Natural successful spawning has not noticeably occurred in these transplanted populations, with the possible exception
Salmon, Coho 167
Salmon, Coho (continued) of the Great Lakes in Michigan; the Great Lakes contain substantial populations of coho, which are sustained through extensive stocking.
Life history/Behavior. Like all species of Pacific salmon, coho are anadromous. They hatch in freshwater rivers, spend part of their lives in the ocean, and then spawn in freshwater. Those coho that have been transplanted to strictly freshwater environments (as in the Great Lakes) hatch in tributary rivers and streams, spend part of their lives in the open water of the lake, and then return to tributaries to spawn. All coho die after spawning.
Adult male sea-run coho salmon generally enter streams when they are either 2 or 3 years old, but adult females do not return to spawn until age 3. The timing of runs into tributaries varies. Coho salmon in Alaska enter spawning streams from July through November, usually during periods of high runoff. In California, the runs occur from September through March, and the bulk of spawning occurs from November through January. Streams throughout the Great Lakes primarily receive coho from late August into October.
Adults hold in pools before moving onto spawning grounds; spawning generally occurs at night. The female digs a nest, or redd, and deposits her eggs, which are fertilized by the male.
Food and feeding habits. Juvenile coho in freshwater feed on plankton, then later eat insects. In the ocean, coho salmon grow rapidly, feeding on a variety of organisms, including herring, pilchards, sand lance, squid, and crustaceans. Likewise, coho that live entirely in freshwater feed on plankton and insects as juveniles and on pelagic freshwater baitfish in the lakes. Alewives and smelt are the primary food items, and, in fact, coho and other salmonids were introduced to the Great Lakes and other inland waters especially to help control massive populations of baitfish, which they consume voraciously and thus quickly grow large, stocky bodies. Like all Pacific salmon, the coho does not feed once it enters freshwater on its spawning run.
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