Information AboutSalmon |
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| cold water fish | |
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or King Salmon is the largest salmon in North America and can grow to 1.5 m (58 inches) in length and to 57 kg (125 pounds) in weight. This specimen shows the jaws drawn into a curved "kype", a Secondary Sex Characteristic typical of many male salmon around spawning time.]] 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 Ocean s, as well as the Great Lakes and other land locked lakes. Typically, salmon are , 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 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 certainly 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.1 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 in any way to the salmonidae. It is found along the southern coastline of Australia and Tasmania . Commonly caught there with large beach nets, its use as a commercial fish has been declining over the last 20 years. LIFE HISTORY OF SALMON , in the lower right the Blood Vessel s surround the Yolk and in the upper left the black eyes are visible, even the little lens]] spinning around the yolk and little oildrops, also the gut, the spine, the main caudal blood vessel, the bladder and the arcs of the gills]] 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.2 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.3 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.4 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. A salmon is basically a white fish. The red pigment is made by algae and single cell organisms, which are eaten by shrimps; the pigment is then stored in their shell and flesh. When salmon eat shrimps they also accumulate the pigment in their fatty tissue. In view of the fact that salmon do not lose the pigment, they will turn red in time. As the diet of salmon differs, a tremendous variety of colours exist in natural salmon, ranging from light pink to deep red. Most salmon these days are cultured. This takes place in large nets in quiet waters (fjords, bays) or in tanks on land. Most cultured salmon come from Norway, Scotland, Iceland, Alaska and Chile. These salmon are mainly fed with fishmeal. This does not contain shrimp, which means the salmon will stay white. The consumer, however, does not want white salmon, even though the taste is the same. For this reason astaxanthin is added to salmon feed. In most cases the astaxanthin is made chemically; alternatively it is extracted from shrimp flour. Another possibility is the use of dried red yeast, which provides the same pigment. However, the synthetic mixture is cheaper Astaxanthin is a carotenoid, meaning it is a compound similar to carotene. Other carotenoids are responsible for the colour of tomatoes, peppers and carrots. Humans also store astaxanthin in fatty tissues, but we do not get enough into our system to turn red. Flamingos owe their red colour to astaxanthin in the same way as salmon do. SALMON AS FOOD |
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