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Atlantic salmon (Salmo salar)

Atlantic salmon - medium or large-sized salmon fish, whose natural range is located in the north of the Atlantic Ocean. The species is represented mainly by sea-run stocks, but there are also resident (lake-resident) populations. This is one of the most valuable commercial species, an important object of sport fishing, an object of artificial reproduction and penn rearing.

Atlantic salmon

The Atlantic salmon range is divided into two parts. The spawning grounds of this fish are found on two continents – in Europe and in North America. In North America, Atlantic salmon inhabit the northwestern part of the continent – from the Connecticut River in the south to the Ungawa Bay in the north of the Canadian province of Quebec. There are also lake-resident populations of salmon in North America.

In Europe, Atlantic salmon is found from the Iberian Peninsula in the west to Kara River flowing from the Urals – in the east. This fish also enters the rivers of some large islands (Newfoundland and Iceland).

In Russia, this species is distributed in the basins of the Baltic, Barents and White seas. There are three isolated ecological forms of this species. They use different rivers for spawning, and their feeding grounds significantly differ in the environmental conditions. The North Atlantic (Atlantic) salmon form is feeding in the northern part of the Atlantic Ocean. The Baltic form is feeding in the brackish water of this highly desalinated inland sea. The freshwater lake-resident form of salmon is found in the Ladoga, Onega and in several smaller lakes of Karelia. The resident salmon used to be present on the Kola Peninsula, in the Imandra Lake, but this stock had probably extinct.

The maximum length of the Atlantic salmon reaches 1.5 m, weight – up to 39 kg. There is information about a fish weighing 103 pounds (47 kg), caught long ago off the coast of Scotland. The life expectancy of salmon can be up to 10-13 years, but now such individuals are rare. In many stocks the most numerous fish have the age of 5-6 years.

Unlike Pacific salmon, the death of the Atlantic salmon after the reproducing is not “programmed” although in reality most fish do not survive till the second spawning. In the rivers of the Murmanskaya Oblast, the percentage of the second time spawners, as a rule, is only about 1% or less, and only in some rivers, up to 3-4%. The maximum percentage of the fish spawning the 2nd time is observed in the Ponoy River, which is probably caused by the predominantly lowland nature of the river.

Atlantic salmon is a valuable commercial fish, whose catches have always been small. In 1936-1940 in the waters of Russia (without the lakes), the catch was 1.0-1.6 thousand metric tons per year, in 1980-1990 it has decreased to 300-600 tons. Later it has decreased even more. In the lakes in 1936-1940 the catch was 60-75 tons per year, in the 1950es – 160-185 tons. By the present time, the lake populations of the Atlantic salmon have drastically reduced their numbers. They are listed in the Red Books (Endangered Species Lists) of the Russian Federation, Karelia and the Leningradskaya Oblast. In the Red Book of the Murmanskaya Oblast the Atlantic salmon is listed among the species that need special attention to their state.

The Atlantic salmon of the Kola Peninsula can spend one to four full years at sea before entering spawning grounds for the first time. In some rivers, and also very rarely found fish that spawn after one summer spent at sea (these small salmon belong to the autumn form of Atlantic salmon). The size and body weight of salmon that spent one year at sea are on average 1-3 kg; 2 years – from 2 to 6 kg (average 3-4 kg); 3 years – from 4 to 9 kg; 4 years (for the Kola River) – from 10 to 13 kg.

Atlantic salmon and silver sea trout (anadromous form of the brown trout) are somewhat similar to each other by appearance; the inexperienced anglers often confuse them. Salmon differs from large brown trout by a more streamlined shape, a caudal fin that is concave at the end, a thinner tail, and shorter upper jaw that does not reach the rear end of the eye. In addition, most salmon do not have spots below the lateral line. The Atlantic salmon also differs in somewhat larger scales: it has 10–15 (sometimes 16, but usually 11–13) rows of scales between the adipose fin and lateral line, and brown trout has 15 to 18 of such rows.

Atlantic salmonThe adult Atlantic salmon entering the rivers are not homogeneous and congeneric; depending on the size, timing of the run, and ripeness of the milt and eggs they are divided into several groups. First of all, salmon have “spring” and “winter” forms. The “spring” fish enter the river at the beginning of summer with mature roe and milt; they prepare for spawning in the same autumn. The “winter” fish enter freshwater from mid-summer to late autumn; some individuals stay in the estuaries and enter the river after wintering, next spring. The «winter» salmon will spend the whole year (or almost a year) in the river and spawn only in the next autumn.

The following scheme was developed for the large Kola Peninsula rivers with numerous stocks. In the populations of small creeks some of these groups could be totally absent. Right after the ice-flood (from mid to the end of May) in the river appear not numerous, but rather large specimens of the zaledka (this means “after the ice”). It is believed that these fish belong to the “winter” salmon that had come in the previous fall and wintered in the estuary of the river. From the end of May, when the water warms up to + 6°С, the zakroika enter the rivers. These are mainly large females, weighing on average 6 to 10 kg. From mid-June, the grilse (the local name – tinda) begins to come in bigger and bigger numbers; these are mostly small males weighing 1-2, rarely up to 3 kg. The peak of the tinda run is usually observed in the beginning of July.

Simultaneously with the small grilse enter a certain number of larger fish, called mezhen’ (this means “low water”). All fish entering in spring and summer have rather ripe milt and eggs; they are preparing for spawning in the autumn of the same year. Most of them belong to the “spring” form of Atlantic salmon, which will become ripe within two to three months. Only the zaledka belongs to “winter” salmon, which had entered fresh water last fall.

The autumnal run of the Atlantic salmon begins in August and continues until freezing. At this time, the osyonka or osen’ (it means “autumn” in Russian) is entering the rivers; the average weight of these fish mainly represented by the females is 5-6 kg, and sometimes reaches more than 16 kg. Together with the osyonka the smaller fish weighing no more than 4 kg, called listopadka (it means “leaf falling”), enter the rivers. All fishes of the autumn run belong to the “winter” form; they appear in the river with poorly developed roe and milt; they are not yet ready to spawn. Before spawning, these salmon will spend a whole year in the river – winter, spring, and next summer.

In general, there is a difference between Atlantic salmon from the rivers of the Barents Sea and the White Sea. On the northern coast predominate the “spring” salmon form, which is often very large. In June, it is not rare to see a fish weighing more than 10 kilograms. Among the rivers with the largest salmon can be listed such basins as the Kola, Pechenga, Bolshaya Zapadnaya Litsa, Vostochnaya Litsa, Yokanga. Every year, salmon weighing more than 20 kg are caught on these rivers. The rivers Ura, Rynda, Kharlovka, and Varzina are also famous for their remarkable trophies.

In the rivers of the White Sea basin, the most common is the “winter” form of salmon: these fish usually enter the river in the second half of summer or in autumn. They spend in fresh water a full year, and are breeding next autumn. The average and maximum sizes of “winter” fish are smaller compared to the “spring” ones, but in such stocks there is a noticeably smaller percentage of small fish with one year of the sea feeding. In the rivers of the Barents Sea the “winter” fish make a very small share, and in some of them they are absent.

After entering freshwater, the salmon gradually become dark, acquiring the spawning colour that resembles the coloring of the parr. In addition, the males grow a large “hook” – a protrusion on the lower jaw named kype. The spawning of the Atlantic salmon takes place in the fall, before freezing, in the areas with a current and pebble bottom. The roe is laid in the redds (nests dug in the bottom) and covered with pebbles.

The abundance of Atlantic salmon is gradually decreasing in many parts of the range, due to the degradation of the river valleys, unsustainable marine harvesting and freshwater poaching. The commercial penn rearing of salmon that has been developing in recent years has proved to be especially harmful. The areas where cages are located are powerful sources of the pollution. Parasitic crustaceans, are mostly bred on “domestic” salmon, also attack wild fish, whose path into the rivers passes by the penns. These parasites and deseases greatly harm wild salmon stocks. After the attack of crustaceans, many fish are infected with microbial and fungal infections and cannot reach the spawning grounds.

Ilya Sherbovich