Salmon
From Wikipedia, the free encyclopedia

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Superorder: Protacanthopterygii
Order: Salmoniformes
Family: Salmonidae

[Photo] Atlantic Salmon (Salmo salar); Deutsch: Atlantik-Lachs. Source: U.S. Fish & Wildlife Service, WO4846-highlights (crop of full image). Date Issued: January 08 2002. Author: William W. Hartley.

Salmon is the common name for several species of fish of the family Salmonidae. Several other fish in the family are called trout. Salmon live in both the Atlantic and Pacific Oceans, as well as the Great Lakes and other land locked lakes.

Typically, 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; research indicates that at least 90% of the fish that spawn in a particular 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. The precise method salmon use to navigate has not been entirely established, though their keen sense of smell is involved. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning, a trait known as semelparity. However, even in those species of salmon that may survive to spawn more than once (iteroparity), post-spawning mortality is quite high (perhaps as high as 40 to 50%.) Those species average about two or, perhaps, three spawning events per individual.

Salmon has long been at the heart of the culture and livelihood of coastal dwellers. Most peoples of the Northern Pacific shore had a ceremony to honor the first return of the year. For many centuries, people caught salmon as they swam upriver to spawn. A famous spearfishing site on the Columbia River at Celilo Falls was inundated after great dams were built on the river. The Ainu, of northern Japan, taught dogs how to catch salmon as they returned to their breeding grounds en masse. Now, salmon are caught in bays and near shore. Drift net fisheries have been banned on the high seas except off Northumberland on the east coast of England.

Salmon population levels are of concern in the Atlantic and in some parts of the Pacific but in northern British Columbia and Alaska stocks are still abundant. The Skeena River alone has millions of wild salmon returning which support commercial fisheries, aboriginal food fisheries, sports fisheries and the area's diverse wildlife on the coast and around communities hundreds of miles inland in the watershed. The Columbia River salmon population is now less than 3% of what it was when Lewis and Clark arrived at the river.

Both Atlantic and Pacific Salmon are important to recreational fishing around the world.

In the southern hemisphere, there is a fish commonly called the Australian salmon but which is a salt water species and not related to the salmonidae. It is found along the southern coastline of Australia and Tasmania. Commonly caught with large beach nets, its use as a commercial fish has been declining over the last 20 years.

History
In order to lay her roe, the female salmon uses her tail fin to excavate a shallow depression, called a redd. The redd may sometimes contain 5,000 eggs covering 30 square feet. The eggs usually range from orange to red in color. One or more males will approach the female in her redd, depositing his sperm, or milt, over the roe. The female then covers the eggs by disturbing the gravel at the upstream edge of the depression before moving on to make another redd. The female will make as many as 7 redds before her supply of eggs is exhausted. The salmon then die within a few days of spawning.

The eggs will 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 natal stream before becoming smolts which are distinguished by their bright silvery colour with scales that are easily rubbed off. It is estimated that only 10% of all salmon eggs survive long enough to reach this stage. The smolt body chemistry changes, allowing them to live in salt water. Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation in the ocean.

The salmon spend one to five years (depending on the species) in the open ocean where they will become sexually mature. The adult salmon returns primarily to its natal stream to spawn. When fish return for the first time they are called whitling in the UK and grilse or peel in Ireland. Prior to spawning, depending on the species, the salmon undergoes changes. They may grow a hump, develop canine teeth, develop a kype (a pronounced curvature of the jaws in male salmon). All will change from the silvery blue of a fresh run fish from the sea to a darker color. Condition tends to deteriorate the longer the fish remain in freshwater, and they then deteriorate further after they spawn becoming known as kelts. Salmon can make amazing journeys, sometimes moving hundreds of miles upstream against strong currents and rapids to reproduce. Chinook and sockeye salmon from central Idaho, for example, travel over 900 miles and climb nearly 7000 feet from the Pacific ocean as they return to spawn.

The age of a salmon can be deduced from the growth rings on its scales, examined under the microscope. Each year, the fish experiences a period of rapid growth, often in summer, and one of slower growth, normally in winter. This results in rings (annuli) analogous to the growth rings visible in a tree trunk. Freshwater growth shows as densely crowded rings, sea growth as widely spaced rings; spawning is marked by significant erosion as body mass is converted into eggs and milt.

Freshwater streams and estuaries provide important habitat for many salmon species. They feed on terrestrial and aquatic insects, amphipods, and other crustaceans while young, and primarily on other fish when older. Eggs are laid in deeper water with larger gravel, and need cool water and good water flow (to supply oxygen) to the developing embryos. Mortality of salmon in the early life stages is usually high due to natural predation and human induced changes in habitat, such as siltation, high water temperatures, low oxygen conditions, loss of stream cover, and reductions in river flow. Estuaries and their associated wetlands provide vital nursery areas for the salmon prior to their departure to the open ocean. Wetlands not only help buffer the estuary from silt and pollutants, but also provide important feeding and hiding areas.

...

Species
The various species of salmon have many names, and varying behaviors.

Atlantic Ocean species
Atlantic ocean species belong to the genus Salmo. They include,

Atlantic salmon or Salmon (Salmo salar), is the species after which all the others are named.

Pacific Ocean species
Pacific species belong to the genus Oncorhynchus, some examples include;

Cherry salmon (Oncorhynchus masu or O. masou) is found only in the western Pacific Ocean in Japan, Korea and Russia and also landlocked in central Taiwan's Chi Chia Wan Stream.
Chinook salmon (Oncorhynchus tshawytscha) is also known locally as King, Tyee, Spring salmon, Quinnat, Tule, or Blackmouth salmon. Chinook are the largest of all Pacific salmon, frequently exceeding 30 lbs. (14 kg).
Chum salmon (Oncorhynchus keta) is known locally as Dog or Calico salmon. This species has the widest geographic range of the Pacific species : south to the Sacramento River in California in the eastern Pacific and the island of Ky??sh?? 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.
Coho salmon (Oncorhynchus kisutch) is also known locally as Silver salmon. This species is found throughout the coastal waters of Alaska and British Columbia and up most clear-running streams and rivers.
Pink salmon (Oncorhynchus gorbuscha), known as humpies in south east Alaska, are found from northern California and Korea, throughout the northern Pacific, and from the Mackenzie River in Canada to the Lena River in Siberia, usually in shorter coastal streams. It is the smallest of the Pacific species, with an average weight of 3.5 to 4 lbs. (1.6 - 1.8 kg).
Sockeye salmon (Oncorhynchus nerka) is known in the USA as Red salmon. This lake-rearing species is found south as far as the Klamath River in California 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. Although most adult Pacific salmon feed on small fish, shrimp and squid; sockeye feed on plankton that they filter through gill rakers.
Steelhead or Steelhead trout or Rainbow trout (Oncorhychus mykiss) are river spawners, usually found in the same rivers that produce chinook, especially the Columbia, Snake, Skeena, and other large rivers on the Pacific Coast. Steelhead have also been introduced into some rivers surrounding the Laurentian Great Lakes.

Other species
Land-locked salmon (Salmo salar sebago) live in a number of lakes in eastern North America. This subspecies of Atlantic Salmon is non-migratory, even when access to the sea is not barred.
Kokanee salmon is a land-locked form of sockeye salmon.
Huchen or Danube salmon (Hucho hucho), the largest permanent fresh water salmonid

Salmon in mythology
In Irish mythology, the hero Fionn mac Cumhaill, leader of the Fianna, gained powers of perception from a salmon. The young Fionn met the poet Finegas near the river Boyne and studied under him. Finegas had spent seven years trying to catch the salmon of knowledge which lived in a pool on the Boyne, for whoever ate the salmon would gain all the knowledge in the world. Eventually he caught it and told the boy to cook it for him. While cooking it Fionn burst a blister on the salmon's skin, burning his thumb, and instinctively put his thumb in his mouth, swallowing a piece of the salmon's skin. This imbued him with the salmon's wisdom.

In Norse mythology, when Loki, god of mischief and strife, tricked Hod the blind god into killing Baldr, god of beauty and light, Loki jumped into a river and transformed himself into a salmon in order to escape punishment from the other gods. When they held out a net to trap him he attempted to leap over it but was caught by Thor who grabbed him by the tail with his hand, and this is why the salmon's tail is tapered.

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

The text in this page is based on the copyrighted Wikipedia article shown in above URL. It is used under the GNU Free Documentation License. You may redistribute it, verbatim or modified, providing that you comply with the terms of the GFDL.