Salmon and trout

Salmon and Trout Facts

Classification:

• Kingdom: Animalia
• Subkingdom: Bilateria
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Osteichthyes
• Order: Saliminiformes (salmonlike fishes)
• Family: Salmonidae (salmon)
• Genus and species: IncludesOncorhynchus kisutch (coho salmon),O. gorbuscha (pink salmon),O. nerka (sockeye salmon),O. tshawytscha (chinook salmon);Salmo salar (Atlantic salmon),S. trutta (brown trout);Salvelinus fontinalis (speckled trout, brook trout),S. namaycush (lake trout)
• Geographical location: United States, Canada, Europe, and Asia
• Habitat: Freshwater lakes, streams and rivers; oceans of the Northern Hemisphere
• Gestational period: Two weeks to two months
• Life span: Six to fifteen years, depending on species
• Special anatomy: Bony skeletons; toothed mouths; caudal, dorsal, pectoral, and ventral fins developed for long swims; a fleshy fin midway between dorsal and tail fins

Salmon, of the family Salmonidae, are valuable Northern Hemisphere food and game fish. Most belong to five species that live in rivers and off coasts of the North Pacific, from California to Alaska and Siberia. A sixth species inhabits the North Atlantic. Salmonids also include trout, graylings, and whitefish. They eat small fish, insects, and crustaceans. Salmon and some trout are anadromous, living in oceans and migrating to freshwater to breed. The Pacific salmon species belong to the genus Oncorhynchus. Different species spawn in the rivers and streams of western North America during the spring (spring run), summer (summer run), and fall (fall run).

Physical Characteristics and Habitats

Salmonids have elongated bodies, small, round, smooth-edged scales, well-developed swimming fins, and a fleshy fin between the dorsal and tail fins. There are five Pacific salmon species: chinook (king), sockeye (red), humpbacked (pink), dog (calico), and coho salmon.

Spring-run chinook salmon swim upstream to spawn. The species has red, oily flesh, and average weights of twenty-three pounds. They live from California to the Bering Strait. Sockeye (red) salmon, also spring run, weigh five to eight pounds, have deep red flesh, and their fins redden during breeding. Like chinooks, they run up to one thousand miles to spawn. Prior to spawning runs, sockeye and chinook salmon store huge quantities of oil for energy to swim upstream. During migration, nest-building, and mating they do not eat.

The other Pacific species are fall run. Spawning closer to the ocean, they do not require a huge oil energy reserve. Pink salmon weigh three to six pounds and are most abundant in Alaska. Dog salmon are not eaten much because their flesh is not tasty. Coho salmon, six to nine pounds, have pink flesh and live from San Francisco to the Puget Sound.

Atlantic (true) salmon, the largest salmonids, have orange-red flesh. Most other fish of their genus (Salmo) are trout. Atlantic salmon weights average twenty pounds. They migrate from ocean to freshwater to spawn in spring or summer. Nonmigrant Atlantic salmon subspecies inhabit lakes in the northern United States. These “landlocked” salmon are smaller than salmon that migrate.

Trout are also salmonids. Sea trout are anadromous, but most species inhabit only freshwater lakes and streams. They eat smaller fishes, crustaceans, and insects. The most important true trout (genus Salmo) is the rainbow trout of the western United States. Chars, of the trout genus Salvelinus, have smaller scales than true trout and inhabit colder North American, Asian, and European waters. The largest char species, lake trout, often weigh twenty-five pounds and have dark gray bodies with yellow-red spots. They inhabit the Great Lakes, Alaska, Labrador, New Brunswick, Vermont, and Maine.

Lives of Salmonids

Chinook salmon are typical anadromous salmonids. In autumn, adults spawn in Pacific Northwest streams, a few feet deep, where females place eggs in nests where fast-running water is rich in oxygen. Then the males squirt milt on them, and the females stir up the stream bottom so that earth and stones cover and protect the eggs, which hatch in two weeks to two months. This start of a new generation precedes the death of the adults by only a few days. After spawning, the dull-colored adults have slimy bodies and ragged fins from their treks to spawning grounds. For a few days they float downstream, tail-first and torpid, until they die. Their bodies wash ashore and become scavenger feed.

Yolk sacs nourish hatchlings for three months and they then become free-swimming. In one or two years, when they are three to five inches long, they swim to the ocean. Predators kill myriad migrants over the six-month trip, but some make it. In the ocean, salmon spend four years eating and growing. Then they swim back to their hatch sites. During salmonid runs, large numbers are caught for canning, but enough get through to restart the cycle. During their runs they leap rapids, waterfalls, and, increasingly, dams. Atlantic salmon survive spawning, return to the ocean, and later reuse the same spawning site several times.

The most widely distributed North American trout species is the brook (speckled) trout, found from Georgia to the Arctic Ocean. They spawn from September to December in holes that females scrape in gravel. Trout eggs take two to three months to hatch, and young develop as do salmon.

Catching and Disseminating Salmonids

In the United States in 2012, US aquaculture production of salmon was 43 million pounds. Fishermen sell them to companies that supply consumers with fresh, frozen, smoked, or canned salmon. When salmon are caught before spawning, their eggs and milt can be removed. To maintain salmon numbers, the US Fish and Wildlife Service yearly collects billions of eggs, fertilizes them and puts the eggs and young in breeding grounds. Trout caught by game and commercial fishermen are sold as food less often than salmon, though they are frequently eaten by their catchers. Their eggs are collected, fertilized, and disseminated by the Fish and Wildlife Service, too. Freshwater and ocean fish farms also produce salmonids.

Principal Terms

anadromous: ocean-dwelling fish that migrate to freshwater to breed

milt: semen that holds sperms from male fishes

seine: a net hanging vertically with floats at its top and weights at its bottom

troll: fish by dragging a baited hook through the water.

Bibliography

Calabi, Silvio. Trout and Salmon of the World. Wellfleet, 1990.

Jonsson, Bror, and Nina Jonsson. Ecology of Atlantic Salmon and Brown Trout: Habitat as a Template for Life Histories. Springer, 2011.

Pennell, William, and Bruce A. Barton. Principles of Salmonid Culture. Elsevier, 1996.

Quinn, Thomas P. The Behavior and Ecology of Pacific Salmon and Trout. American Fisheries Society, 2005.

Stolz, Judith, and Judith Schnell. Trout. Stackpole Books, 1991.

Watson, Rupert. Salmon, Trout, and Char of the World: A Fisherman’s Natural History. Small Hill, 1999.