The Salmon Fish

Fish World | The Salmon Fish | Salmon is the common name for several species of fish in the Salmonidae. Several other fish in the same family are called trout, the difference is often said to be the migrating salmon and trout are resident, but this distinction is not strictly hold true. Salmon live along the coasts of both North Atlantic (one migratory species Salmo salar) and Pacific (approximately a dozen species of the genus Oncorhynchus), and have also been introduced in the Great Lakes of North America. Salmon are extensively produced in aquaculture in many parts of the world.

Typically, salmon are anadromous: they are born in freshwater, migrate to the ocean, then return to fresh water to reproduce. However, there are populations of different species to fresh water is limited by their lives. Folklore has it that the fish return to the exact spot where they were born to spawn, tracking studies have shown that this is true, and this homing behavior is shown to depend on olfactory memory.

Salmon eggs are laid in freshwater streams usually at high latitudes. The eggs hatch into alevin or sac boy. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts which are distinguished by their bright silver color with scales that are easily rubbed off. It is estimated that only 10% of all salmon eggs survive this stage. The smolt body chemistry changes, so they live in salt water. Smolts spend some of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation in the ocean.
The salmon spend about one to five years (depending on the species) in the open ocean, where they gradually become sexually mature. The adult salmon return to their home especially stream to spawn. In Alaska, the crossing-over to other salmon streams can populate new streams, such as a glacier retreats created. The precise method salmon use to navigate has not been determined, although their sense of smell is involved. Atlantic salmon spend between one and four years at sea. (When a fish returning from sea just one year to feed a grilse in Canada, Great Britain and Ireland called.) Just before spawning, depending on the species, salmon changes. They may grow a hump, develop canine teeth, develop a kype (a pronounced curvature of the jaws in male salmon). 

Everything will change from the silvery blue of a fresh fish away from the sea to a darker color. 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 (1.400 km) and nearly 7,000 feet (2,100 m) of the Pacific when they return to spawn climb. Condition tends to deteriorate the longer the fish remain in fresh water, and they then deteriorate further after they spawn, as they are known as Celts. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning, a trait known as semelparity. Between 2% and 4% of the Celts Atlantic salmon survive to spawn again, all women. But even in those species of salmon that may survive to more than once (iteroparity) spawn, post-spawning mortality is quite high (perhaps as high as 40-50%.)
To lay her roe, the female salmon uses her tail (caudal fin), creating a low pressure area, lifting gravel are swept downstream, dig a shallow depression, called REDD. REDD may sometimes contain 5,000 eggs 30 square feet (2.8 m2). The eggs usually range from orange to red. One or more males approach the woman in the REDD, pouring his sperm, or spleen, the deer. The female then covers the eggs by disturbing the gravel at the upstream side of the depression before moving on to another to make REDD. The female will only seven redds before her supply of eggs is exhausted.

Each year, the fish experiences a period of rapid growth, often in the summer, and one of the slower growth, usually in winter. This results in the formation of a ring around earbone called the otolith, (annuli) analogous to the growth rings visible in a tree. Freshwater growth shows as densely crowded ring, sea growth as widely spaced rings, spawning is marked by significant erosion as body mass is converted into eggs and spleen.
Freshwater rivers and estuaries provide important habitat for many species of salmon. They feed on terrestrial and aquatic insects, amphipods and other crustaceans while young, especially 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 salinity, high water temperatures, low oxygen concentration, loss of stream cover, and the reduction of river flows. Estuaries and their associations wetlands provide vital nursery areas for salmon prior to their departure to the open ocean. Wetlands not only help buffer the estuary from silt and pollutants, but also important feeding and hiding areas.

Salmon that are not slain by a different way greatly accelerated deterioration (phenoptosis, or "programmed aging") at the end of their lives. Their bodies rapidly, immediately after the deposition due to the release of large amounts of corticosteroids.

Eosalmo driftwood ensis, the oldest known fossil salmon in the fossil record, helps scientists figure how different types of salmon diverged from a common ancestor. The British Columbia Salmon fossil provides evidence that the difference between Pacific and Atlantic salmon had not occurred 40 million years ago. Both the fossils and the analysis of mitochondrial DNA suggest that the divergence caused by 10 to 20 million years ago. This independent evidence from fossils and DNA analysis reject the theory of glacial salmon divergence.

The salmon has long been at the heart of the culture and livelihood of coastal dwellers. Many people of the northern Pacific coast was a ceremony to return the first of the year honor. For many centuries, people caught salmon as they swim upstream 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 in northern Japan, trained dogs to catch salmon as they return to their breeding grounds en masse. Now salmon caught in bays and near shore.

Salmon population levels are important in the Atlantic Ocean and in parts of the Pacific Ocean. Alaska stocks are still abundant and the catches are on the rise in recent decades, after the state initiated restrictions in 1972. Some of the key sustainable Alaskan salmon fishery would be located near the Kenai River, Copper River and Bristol Bay. Fish farming of Pacific salmon is prohibited in the United States Exclusive Economic Zone, but there is a large network of publicly funded hatcheries, and the State of Alaska fisheries management system is seen as a leader in the management of wild stocks. In Canada, back Skeena River wild salmon support commercial, subsistence and recreational fisheries, and the various wildlife area on the coast and around communities hundreds of miles inland in the catchment. The status of wild salmon in Washington is mixed. Of the 435 wild stocks of salmon and steelhead, only 187 of them were classified as healthy, 113 with unknown status, an extinct, 12 were in critical condition and 122 were experiencing depressed populations. The Columbia River salmon population is now less than 3% of what it was when Lewis and Clark arrived at the river. The commercial salmon fishery in California are either severely restricted or completely closed in recent years, due to critically low return on the Klamath and Sacramento Rivers or so millions of dollars in losses to commercial fishermen.  Both the Atlantic and Pacific salmon are popular sportfish.

Salmon populations now exist in all the Great Lakes. Coho stocks were planted in the late 1960s in response to the growing population of non-native Alewife by the state of Michigan. Now, Chinook (King), Atlantic and Coho (silver) salmon are stocked annually in all Great Lakes by the most adjacent states and provinces. These populations are not self-sufficient and not much to offer in the way of a commercial fishery, but have led to the development of a thriving sportfishery.