Salmon Essay -- essays research papers

The upriver salmon migration is one of nature's most exciting dramas. But to the five species of Pacific salmon (Chinook , chum, coho, pink, and sockeye), it is a long, strenuous, desperate race against time, with every obstacle taking its toll. Pacific salmon belong to a group called anadromous fish that includes Atlantic salmon, sturgeon, lampreys, shad, herring, sea- run cutthroat trout, and steelhead trout. These species hatch and live the first part of their lives in fresh water, then migrate to the ocean to spend their adult lives, which may be as short as 6 months or as long as 7 years. When they reach sexual maturity, they return to the freshwater stream of their origin to lay their eggs. Pacific salmon make the round trip only once, but some Atlantic salmon may repeat the cycle several times. Migration between fresh and salt water occurs during every season of the year, depending on latitude and genetic characteristics of the fish. Groups of fish that migrate together are called runs or stocks. Salmon spawn in virtually all types of freshwater habitat, from intertidal areas to high mountain streams. Pacific salmon may swim hundreds, even thousands, of miles to get back to the stream where they hatched. However, only a small percentage of salmon live to reach their natal stream or spawning grounds. Those males that survive the trip are often gaunt, with grotesquely humped backs, hooked jaws, and battle-torn fins. The females are swollen with a pound or more of eggs. Both have large white patches of bruised skin on their backs and sides. Since salmon do not feed once they leave the ocean, some will die on the way because they lack enough stored body fat to make the trip. Many will be caught in fishermen's nets. Those that evade the nets may have to swim through polluted waters near cities. Many must make their way over power dams, leaping up from one tiny pool to the next along cement stairstep cascades called fish ladders. In the tributary streams, waterfalls and rapids are steep and swift enough to eliminate all but the strongest. Otters, eagles, and bears stalk the salmon in shallow riffles. Once on the spawning grounds, the fish battle each other: females against females for places to nest, males against males for available females. The female builds her nest, called a redd, by agitating the bottom gravel with her fins and tail, and bending ... ...almon belong to the Department of Commerce's National Marine Fisheries Service. The U.S. Fish and Wildlife Service and other federal and state agencies also have recovery responsibilities. The largest of the Pacific salmon, chinook (Oncorhynchus tshawytscha) average about 24 pounds when they return to their natal river to spawn, most after 2 or 3 years at sea. The chinook is the least abundant of the Pacific salmon. Coho salmon (Oncorhynchus kisutch), fourth in Pacific fishery abundance, is the number one sport fish. It spends only one winter at sea, returning the next fall to spawn. It averages about 10 pounds when full grown. Sockeye salmon (Oncorhynchus nerka) make up about 25 percent of the West Coast catch, and chum salmon (Oncorhynchus keta) make up about 13 percent. Both follow similar migration paths in the Pacific and reach a common weight of about 12 pounds before returning to their natal river to spawn. Pink salmon (Oncorhynchus gorbuscha), the smallest of the Pacific salmon, average only about 3 to 5 pounds. However, they make up more than half the total West Coast commercial catch. Pink salmon seldom travel more than 150 miles from the mouth of their natal river.