Salmon

Salmon, << SAM uhn, >> is one of the most important food and sport fishes. Every year, people throughout the world eat millions of cans of pink or red salmon. Fishing enthusiasts also catch millions of salmon yearly.

Most of the salmon sold comes from five species (kinds) that live in the coastal waters of the North Pacific Ocean. Two other Pacific species live only in northern Asian waters. One species, called the Atlantic salmon, lives in the North Atlantic Ocean. This fish is not closely related to the salmon in the Pacific Ocean.

Salmon are born in a freshwater stream or lake, and most spend part of their life in the salt water of the ocean. They then return to the freshwater area of their birth to spawn (reproduce). Most Pacific salmon spawn only once and die soon afterward. Atlantic salmon may swim back to the ocean after spawning and return to fresh water to spawn as many as three more times. Some salmon are landlocked (cut off from the ocean) in lakes and streams. Adult salmon swim upstream at spawning time. The fish are famous for their fighting spirit. They battle currents and leap across rapids and up waterfalls as high as 10 feet (3 meters). When hooked, they struggle furiously to escape.

The life of a salmon.

Most salmon spawn during the summer or autumn after swimming upstream as far as 2,000 miles (3,200 kilometers) from the ocean. The journey may take several months. Female salmon lay their eggs in the gravelly bed of a shallow, rippling stream or at beaches along lakeshores. A male salmon stands guard as the female turns on her side and digs a saucer-shaped nest in the gravel by swishing her tail back and forth. The female lays her eggs in the nest, and the male fertilizes them with sperm. The female then swims forward a short distance, digs another nest, and lays more eggs. The spawning process may occur several times. The gravel dug from each nest normally washes back and covers the previously laid eggs. During spawning, the female lays a total of 2,000 to 17,000 eggs.

The eggs hatch after two to four months, and the baby salmon lie hidden in the gravel for up to several more months. They feed on a yolk sac (a baglike structure containing food materials) attached to their stomach. Some kinds of salmon leave fresh water for the ocean immediately after they come out of the gravel. Other species may spend up to three years in fresh water. They eat insects and water organisms called plankton.

Only a small percentage of the salmon reach the ocean from fresh water. Fish and birds eat some salmon, and polluted water kills others. Many of the salmon die in huge artificially created reservoirs.

Salmon that reach the ocean live there from six months to seven years. During this period, they feed mainly on shrimp, squid, and small fishes. Some salmon travel thousands of miles or kilometers from the river where they were born. But most salmon return for spawning to the same stream or lake in which they hatched. Many scientists think salmon navigate in the sea by somehow sensing the magnetic field of the earth, the currents of the ocean, and the position of the sun. After reaching the coast, the salmon apparently remember the odor of their “home” stream and follow this scent.

Salmon stop eating after reaching fresh water to spawn. They live off fat stored in their body. As the fish travel upstream, their shape and color change. For example, all male salmon develop a hooked snout. Male pink salmon grow a large hump on their back. Chum salmon of both sexes develop purple streaks on their sides, and sockeye salmon turn bright red.

Many salmon do not complete the spawning journey. Commercial fishing crews and sports enthusiasts catch large numbers of the fish. Some salmon are killed by pollutants dumped into the rivers by industries. Artificial sloping waterfalls called fish ladders have been built to help salmon travel over dams. But some salmon become so weakened climbing the ladders that they die.

Kinds of salmon.

There are eight species of salmon: (1) amago, (2) Atlantic, (3) cherry, (4) chinook, (5) chum, (6) coho, (7) pink, and (8) sockeye. All except Atlantic salmon live in the Pacific Ocean.

Amago salmon,

the smallest species, grow only about 5 to 9 inches (12 to 24 centimeters) long. They live in southern Japan.

Atlantic salmon

are not nearly so plentiful as Pacific salmon and have much less commercial importance. Most Atlantic salmon measure about 2¹/₂ feet (75 centimeters) long and weigh about 10 pounds (4.5 kilograms).

Cherry salmon,

or masu salmon, live in coastal waters and rivers of eastern Asia. They vary in length from about 16 to 28 inches (40 to 70 centimeters) and weigh from 5 to 23 pounds (2.3 to 10 kilograms).

Chinook salmon,

the largest species, are also known as blackmouth, king, quinnat, spring, tule, or tyee salmon. Most chinooks are about 3 feet (90 centimeters) long and weigh about 22 pounds (10 kilograms).

Chum salmon

are also called calico, dog, or keta salmon. They grow about 2 feet (60 centimeters) long and weigh about 10 pounds (4.5 kilograms).

Coho salmon

are also known as medium red, silver, or silverside salmon. They are about 2 feet (60 centimeters) long and weigh about 10 pounds (4.5 kilograms). Scientists have introduced cohos into the Great Lakes. The salmon provide fishing and help control the number of alewives. See Alewife .

Pink salmon,

or humpback salmon, grow about 20 inches (50 centimeters) long. They weigh about 5 pounds (2.3 kilograms).

Sockeye salmon,

also known as blueback or red salmon, are the most valuable food salmon. A sockeye measures about 2 feet (60 centimeters) long and weighs about 6 pounds (2.7 kilograms). Kokanee salmon are a landlocked variety of sockeye salmon.

Salmon fishing.

After salmon enter fresh water, their flesh loses flavor and color. Therefore, commercial fishing crews catch salmon as the fish leave the ocean to journey upstream. Most salmon are caught in nets. Some salmon is sold fresh, frozen, or smoked, but most is canned. Salmon fishing and processing rank as major industries in Alaska, Oregon, and Washington, and in the Canadian province of British Columbia. Fish farms in these areas also produce much Pacific salmon.

Sport fishing for salmon is popular in the United States and Canada. Coastal waters, lakes, and rivers in many parts of the world have been stocked with salmon. But transplanted salmon thrive only in a few places, such as the Great Lakes and New Zealand.

Salmon conservation

is based on the theory that a certain number of fish, called the escapement, should be allowed to spawn in each stream. Fishing is regulated to ensure the proper escapement. Conservation programs must also overcome such obstacles as dams, irrigation ditches, and pollution. In many areas, including northwestern North America, overfishing and other factors have sharply cut the salmon populations.

The most important advance in conservation has been the development of improved hatcheries. These hatcheries, helped by increasing knowledge of fish nutrition and diseases, can produce thousands of healthy salmon to restock rivers and streams. Other conservation efforts have resulted in new designs for dams and fish ladders. Artificial spawning channels, with controlled water flow and temperature, have also been developed.