Salmon Sockeye

Oncorhynchus nerka

Sockeye Salmon

(spawning male)

Kokanee Salmon

A member of the Salmonidae family, the sockeye is like some other members of the Pacific salmon group, in having both anadromous and freshwater forms. The former migrate from freshwater streams to the ocean and then return to those streams to spawn, whereas the latter remain in freshwater all their lives. Called kokanee, the freshwater form was once thought to be the subspecies O. kennerlyi but is now accepted as the same species with characteristics identical to that of the anadromous sockeye, although it is a smaller fish. It occurred naturally in some waters in the drainages of the Pacific and has been spread through stocking to many other waters. Kokanee can be fine gamefish and excellent food fish; sockeye salmon are predominantly prized more for their food value than for sport, however, as the upstream migrants are not aggressive at taking bait or lures.

Identification. The sockeye is the slimmest and most streamlined of Pacific salmon, particularly immature and pre-spawning fish, which are elongate and somewhat laterally compressed. They are metallic green-blue on the back and the top of their heads, iridescent silver on the sides, and white or silvery on the bellies. Some fine black speckling may occur on their backs, but large spots are absent.

Breeding males develop humped backs and elongated, hooked jaws filled with sharp, enlarged teeth. Both sexes turn brilliant to dark red on their backs and sides, pale to olive green on their heads and upper jaws, and white on the lower jaws. The totally red body distinguishes the sockeye from the otherwise similar chum salmon, and the lack of large distinct spots distinguishes it from the remaining three Pacific salmon of North America. The number and the shape of gill rakers on the first gill arch further distinguish the sockeye from the chum salmon; the sockeye salmon has 28 to 40 long, slender, rough or serrated closely set rakers

OTHER NAMES

sockeye, red salmon, blue-back salmon, big redfish; French: saumon nerka; Japanese: benizake, himemasu. The landlocked form is called kokanee salmon, Kennerly's salmon, kokanee, landlocked sock-eye, kickininee, little red-fish, silver trout; French: kokani.

Distribution. The sockeye salmon is native to the northern Pacific Ocean and its tributaries from northern Hokkaido, Japan, to the Anadyr River, Russia, and from the Sacramento River, California, to Point Hope, Alaska. Kokanee exist in Japan, Russia, Alaska, at least three western provinces in Canada, seven western U.S. states, and three eastern states.

Habitat. Sockeye salmon are anadromous, living in the sea and entering freshwater to spawn. They mainly enter rivers and streams that have lakes at their source. Young fish may inhabit lakes for as many as

Salmon, Sockeye 171

Salmon, Sockeye (continued) 4 years before returning to the ocean. Kokanee occur almost exclusively in freshwater lakes, migrating to tributaries in the fall to spawn (or to outlet areas or shoreline gravel in waters without suitable spawning streams).

on the first arch, whereas the chum salmon has 19 to 26 short, stout, smooth rakers.

Kokanee are smaller but otherwise identical to sea-run sockeye in coloration; they undergo the same changes as sockeye do when spawning.

Size. Adult sockeye usually weigh between 4 and 8 pounds. The all-tackle world record is an Alaskan fish that weighed 15 pounds, 3 ounces. Kokanee are much smaller; in many places they do not grow much over 14 inches or 1 pound, especially where the plankton food resource is low or where many other species compete for it; the all-tackle world record is a British Columbia fish that weighed 9 pounds, 6 ounces.

Life history/Behavior. Sockeye salmon return to their natal streams to spawn after spending 1 to 4 years in the ocean. They enter freshwater systems from the ocean during the summer months or the fall, some having traveled thousands of miles. Most populations show little variation in their arrival time on the spawning grounds from year to year; kokanee spawn from August through February, sockeye from July through December.

Eggs hatch during the winter, and the young alevins remain in the gravel, living off the material stored in their yolk sacs until early spring. At this time they emerge from the gravel as fry and move into rearing areas. In systems with lakes, juveniles usually spend 1 to 3 years in freshwater before migrating to the ocean in the spring as smolts weighing only a few ounces. In systems without lakes, however, many juveniles migrate to the ocean soon after emerging from the gravel.

Although most sockeye salmon production results from the spawning of wild populations, some runs have been developed or enhanced through human effort.

Food and feeding habits. Anadromous salmon rarely feed after entering freshwater, although young fish will feed mainly on plankton and insects. In the ocean, sockeye salmon feed on plankton, plus on crustacean larvae, on larval and small adult fish, and occasionally on squid. Kokanee feed mainly on plankton but also on insects and bottom organisms.

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