[Atlantic salmon articles]
Common name: Atlantic salmon
Latin name: Salmo salar
Record weight: One of the oldest records on the books, and one that is very unlikely to be beaten in the future. The Atlantic salmon is the second largest fish (behind the wels catfish) found in British freshwaters with a record weight of 64lb caught By Miss G.W. Ballantine in 1922.
Distribution: Salmon are an anadromous species that lay their eggs in freshwaters, then migrate as juveniles to the sea where they grow and mature before returning to freshwaters to spawn. Although salmon tend to return to their stream of birth to lay their eggs some do get lost and so they spread quite quickly. The main limit to their spread in present times is warm water. Salmon are most at home in the cool streams of Northern Europe and Canada and so are found as far South as the mountain streams of the Massif Centrale in France. Once common throughout the rivers of the UK, salmon are now mostly limited to the rivers of the West and North of the country, where pollution and weirs have not impacted so severely on the young fish.
Features: A silvery fish with steely blue spots on fresh fish. Quite similar to fresh run sea trout (Salmo trutta) one simple means of identifying salmon is to try to pick the fish up by the root of the tail. The salmon has a distinct narrowing here which allows it to be handled easily.
Diet: In the sea, adult salmon feed upon small fish and crustaceans, particularly sandeels and juvenile herring. In freshwaters, adult salmon do not feed and must spend several weeks or months travelling to the spawning streams without nourishment. Young salmon feed upon small invertebrates, particularly freshwater shrimps and caddis larvae. Juvenile salmon tend to be highly nocturnal, particularly in the Winter months when the risk of predation by herons is high during daylight.
Spawning: Adult salmon tend to enter the river in two distinct waves. The largest fish tend to enter the river during the Spring and make their way quite quickly upstream to spawn. The second run of salmon occurs in the Autumn just prior to spawning in November and December. When conditions are right, the female excavates a large area of gravel in shallow fast flowing water. The gravel, known as a redd, can be several feet in diameter and more than twelve inches deep. The female lays her eggs in the redd where they are fertilised by the male fish. The female then moves upstream and covers the eggs with more gravel so that they are buried deep within the bed of the river. The eggs take several months to hatch in the cool water of Winter streams. Once hatched, the larval salmon have a large yolk sack that sustains them for several more weeks before they need to start hunting small invertebrates, still deep within the gravel. When the salmon finally emerge from the gravel after approximately a month they are known as parr and are fully formed fish that grow rapidly during the warmer Summer months.
Growth: The growth of salmon is highly variable both within a stream and between streams. Young salmon spend up to three years in their natal streams before migrating to the sea. In some environments a small percentage of the male salmon do not migrate to sea. These males remain no more than twelve inches in length and are called sneaker males as they will sneak in and spawn with the much larger females. Generally though, the salmon spend between one and four years at sea before returning to spawn. Most fish will die as a result of the rigours of making their way upstream and spawning, but around ten percent will survive and return to the sea for another period of growth before returning again. Very large salmon are now very rare as a result of over-fishing of the small number of returning fish.