Science Fair Project Encyclopedia
- This article is about the fish. For the color, see salmon (color).
Salmon are anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce. Folklore has it that the fish return to the exact spot where they were born to spawn and modern research shows that usually at least 90% of the fish spawning in a stream were born there. In Alaska, the crossing over to other streams allows salmon to populate new streams, such as those that emerge as a glacier retreats. How they navigate is still a mystery, though their keen sense of smell may be involved. In all species of Pacific salmon, the mature individuals die within a few weeks of spawning.
Coastal dwellers have long respected the salmon. Most peoples of the Northern Pacific shores had a ceremony to honor the first return of the year. For many centuries, people caught the salmon as they swam upriver. A famous spearfishing site on the Columbia River at Celilo Falls was inundated after great dams were built on the river. Now, salmon are caught in bays and near shore. Long drift net fisheries have been banned on the high seas except off the coast of Ireland.
Both Atlantic and Pacific Salmon are important to recreational fishing around the world.
The female salmon lays fertilized eggs in stream bottom gravel nests called redds. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for one to three years in their native stream before becoming smolts. The smolt body chemistry changes allowing them to live in salt water. They migrate to the ocean where they will develop in about two to three years into mature salmon. The adult salmon will return to their native stream to repeat the spawning cycle. Once the adult spawns, it is called a kelt and often dies. If it survives, it will repeat the migration and spawning cycle.
Salmon as Food
Salmon is a popular food, and reasonably healthy due to its high protein and Omega-3 fatty acids and its overall low fat levels. According to reports by Science, however, farmed salmon may contain high levels of dioxins. PCB (Polychlorinated biphenyl) levels may also be up to 8 times higher in farmed salmon compared to wild salmon, and Omega-3 content may also be lower than wild caught species. But according to the British FSA (Food Standards Agency) the benefits of eating even farmed salmon still outweigh the risks. Conversely, salmon is generally one of the least tainted by methyl mercury of all fish.
A simple rule of thumb is that the vast majority of Atlantic salmon available on the world market is farmed (greater than 99%), whereas the majority of Pacific salmon is wild-caught (greater than 80%).
Salmon is a white-flesh fish. The natural color of salmon results from carotenoids -- astaxanthin and to a lesser degree, canthaxanthin -- in the fish flesh. Wild salmon get these carotenoids from eating krill and other tiny shellfish. Farm salmon get them in their feed, along with other essential nutrients. It is important to note that astaxanthin is a potent antioxidant that also stimulates fish nervous systems and improves fertility and growth.
Canned salmon in the U.S. is always wild Pacific catch. Smoked salmon is another popular preparation method, and can either be hot or cold smoked. Lox can refer either to cold smoked salmon, or to salmon cured in a brine solution (also called gravlax).
Raw salmon meat may contain anisakidae , a marine parasite to cause anasakiasis . Before the availability of refrigeration, Japanese did not consume raw salmon. Salmon and salmon roes were not used to make sashimi (raw fish) and sushi until recently.
Salmon is the second largest seafood product raised on fish farms, with shrimp being the largest product. Raising salmon on farms decreases the demand for wild salmon but paradoxically increases the demand for other wild fish. Salmon are carnivorous and are currently fed a meal produced from catching other wild fish, so as the number of farmed salmon increase, the demand for other fish to feed the salmon increases. Work continues on substituting vegetable proteins for animal proteins in the salmon diet.
The various species of salmon have many names.
Atlantic Ocean species
- Salmo salar is the Atlantic Salmon or just Salmon, the species after which the others are named. It breeds in the rivers of western Europe from northern Portugal north to arctic Norway, Iceland, Greenland, and the east coast of North America from Connecticut in the United States north to northern Labrador in arctic Canada. At sea, it is found mainly in the waters off Greenland.
- However, the wild atlantic salmon fishery is commercially dead; after extensive habitat damage and overfishing, wild fish make up only half of one percent of the atlantic salmon available in world fish markets. The rest are farmed, predominantly from aquaculture in Chile, Canada, Norway, and the U.K..
- Another Atlantic species, Salmo trutta, is usually classified as a trout, despite being a closer relative of Atlantic Salmon than any of the Pacific species of salmon. See Brown Trout.
Pacific Ocean species
- Oncorhynchus nerka is called Sockeye Salmon, or locally "Red Salmon" or "Blueback Salmon." This species is found south as far as the Klamath River in California in the eastern Pacific and northern Hokkaido 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.
- 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 the Sockeye's flesh.
- 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.
- This species is netted for commercial 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 is sold frozen.
- Oncorhynchus tshawytscha is called Chinook Salmon, or locally, King, Tyee, Spring Salmon, Quinnat, Tule, or Blackmouth. This species grows to a great size and may migrate for hundreds or thousands of miles up freshwater rivers to spawn. The young live in freshwater as fry for some time. Maturity occurs between the second and seventh year of life.
- Chinook salmon are also called 'King Salmon' because many consider them to be the best tasting. Those from the Copper River in Alaska are particularly known for their color, flavor, firm texture, and high Omega-3 oil content.
- Oncorhynchus gorbuscha is called Pink or Humpback Salmon. This species is found from northern California and Korea, throughout the northern Pacific, and from the Mackenzie River in Canada to the Lena River in Siberia.
- The young hatch by mid-winter and migrate to the ocean by spring. They move into the deep ocean in the fall where they stay for two years. When mature, the pink salmons return to spawn close to the coast, some in intertidal areas.
- Beginning in the late nineteenth century, fish traps were used to supply fish for commercial canning and salting. The industry expanded steadily until 1920. During the 1940s and 1950s, Pink Salmon populations declined drastically. Fish traps were prohibited in Alaska in 1959. Now most pink salmon are taken with purse seines and drift or set gillnets. Some increase in population is evident.
- Oncorhynchus keta is called Chum Salmon, or locally, Dog or Calico. This species has a wide geographic range: south to the Sacramento River in California in the eastern Pacific and the island of Kyushu in the Sea of Japan in the western Pacific; north to the Mackenzie River in Canada in the east and to the Lena River in Siberia in the west.
- Most Chum Salmon spawn in small streams and intertidal zones, especially among stalks of eelgrass. The young feed on small insects in streams and estuaries, then move out to saltwater in the fall. They mature after three, four, five, or six years. Some Chum travel more than 3,200 km (2,000 miles) up the Yukon River.
- Oncorhynchus kisutch (Walbaum) is called Coho Salmon or Silver Salmon. This species is found throughout the coastal waters of Alaska and up most clear-running streams and rivers. The eggs hatch in the spring. Young often spend the first winter in off-channel sloughs. Some fish leave fresh water in the spring, spend summer in brackish estuarine ponds and then migrate back into fresh water in the fall. Coho spend one to three winters in streams (or up to five winters in lakes) before migrating to the sea.
- This species is a fighting fish and provides fine sport in fresh and salt water from July to September, especially with light tackle.
- Alaska Deptartment of Fish & Game Wildlife Notebook Series
- http://www.critfc.org/ Tribal Salmon Restoration Plan
- How to fish for salmon
- Salmon Nation A place and idea for "reliable prosperity."
- Salmon fishing in Alaska
- Nutrition information for cooked and smoked salmon
- Seafood Watch executive report on farmed Atlantic salmon from the Monterey Bay Aquarium
- Stores Say Wild Salmon, but Tests Say Farm Bred
- Is Something Fishy Going On?
- Atlas of Pacific Salmon, Xanthippe Augerot and the State of the Salmon Consortium, University of California Press, 2005, hardcover, 152 pages, ISBN 0-520-24504-0
- Trout and Salmon of North America, Robert J. Behnke , Illustrated by Joseph R. Tomelleri, The Free Press, 2002, hardcover, 359 pages, ISBN 0-7432-2220-2
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