Sockeye salmon
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[Photo] Sockeye salmon (Oncorhynchus nerka). Photo by Timothy Knepp of the Fish and Wildlife Service.

Sockeye salmon (Oncorhynchus nerka), also called red salmon or blueback salmon, is an anadromous species of salmon found in the Pacific Ocean. The same species when it occurs in landlocked bodies of water is called the kokanee. This species is the third most common type of Pacific salmon, after Pink and Chum salmon.

Range
Its current range is as far south as the Columbia River in the eastern Pacific and northern Hokkaid?? Island in Japan in the western Pacific, and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Landlocked populations occur in the Yukon Territory and British Columbia in Canada, and in Alaska, Washington, Oregon, California, Utah, Idaho, Montana, Colorado,New Mexico, and Wyoming in the United States.

Physical Description
A Sockeye can be as long as 33 inches (84 cm) and weigh 6 to 8 pounds (2.5 to 3.5 kilos). It has an elongated, torpedo shaped body, with an adipose fin, and a bluntly pointed snout. The gill rakers located just behind the head are long and closely spaced. Its colouration changes as it migrates from saltwater to freshwater in preparation for spawning. In freshwater, its colour is bright red with a pale green head; females may have green and yellow marks or stains. Its colour in saltwater is bluish-green on top, silvery on the bottom, with uniform, shiny skin.

Reproduction
Prior to spawning the sockeye are blue tinged with silver in color during their ocean life. The males develop a hump on their back and their jaw and teeth become hooked when they move from salt to fresh water. Males and females both turn red with green heads, and a dark stripe on their sides prior to spawning.

Sockeye salmon spawn mostly in streams having lakes in their watershed. The young fish, known as fry, spend from zero to three years in the freshwater lake before migrating to the ocean, some stay in the lake and do not migrate to the sea. The fish that migrate spend from one to four years in the salt water, and thus are four to six years old when they return to spawn in autumn (September-December). Migration back to the home river, is thought to be done using the characteristic smell of the stream, and possibly the sun.

Some young fish spend as long as four years in fresh water lakes before migrating to the sea. In rivers without lakes, many of the young move to the ocean quite soon after hatching. These salmon mature after one to four years in the ocean. Some Sockeye Salmon live and reproduce in lakes and are called "kokanee." They are much smaller than the ones that go to the ocean and are rarely over 350mm (14 inches) long.

Ecology/Behaviour
Sockeyes, unlike the other species of Pacific Salmon, feed almost exclusively on plankton. They are able to do this as a result of their many gill rakers, which strain the plankton from the water. It is speculated that this diet is the reason for the striking hue of their flesh as well as their very low concentration of methyl mercury. They also tend to feed on small aquatic organisms such as shrimp.

Sockeye salmon are currently listed under the U.S. Endangered Species Act with the National Marine Fisheries Service as an endangered species in Snake River (Idaho, Oregon and Washington area) and as a threatened species in Lake Ozette, Washington. Other sockeye populations in the upper Columbia River and in Puget Sound (Washington) are not listed under the Endangered Species Act.

Commerce
This species is netted commercially using seines and gillnets for fresh or frozen fillet sales and canning, especially in Bristol Bay, Alaska, site of the largest harvest of sockeye salmon in the world, according to the Alaska Department of Fish and Game. The species has been preferred for canning due to the rich orange-red color of the flesh. More than half of the sockeye salmon caught today are sold frozen. Sockeye also tends to fetch a higher price than other salmon when sold fresh, as they are considered the most flavorful and flexible of the family.

When smoked, Sockeye has a stronger flavour and firmer texture than Coho salmon. Sockeye salmon is a popular sportfish for flyfishermen. It can be caught on a fly-rod when it returns to freshwater to spawn and is an acrobatic and powerful fighter.

http://en.wikipedia.org/wiki/Sockeye_salmon

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