Arctic charr

(Salvelinus alpinus)

Order: Salmoniformes Family: Salmonidae Subfamily: Salmoninae

Description: The Arctic charr is a slender, streamlined, pale silvery grey predator with small scales. At spawning time, the colouration is particularly beautiful, the belly ranging from orange to deep red. Its back is dark, with shades of blue or green. Its sides are flecked with yellowish or reddish spots, and the fins typically have white fore-edges. Unlike the lake trout (Salvelinus namaycush) and brook trout (Salvelinus fontinalis), the Arctic charr has no light spots on its dorsal and anal fins. Neither does it have a mosaic pattern on its dorsal side.

Origin and distribution: The Arctic charr occurs throughout the Arctic and Subarctic, having the most northerly distribution of any freshwater fish species in the world. It can be regarded as a pioneer species, because after the last glaciation it, together with the brown trout (Salmo trutta), was the first species to inhabit the catchments created by the melting ice. The Arctic charr requires cold, oxygenous and clear water. It usually lives in lakes, but is also found in mountain brooks. In Finland, it occurs mainly in the north of the country, in the northernmost Lapland. The only southern exception is the stock in the Vuoksi water system, in the east of the country, where part of the original stock still remains.

The Arctic charr is a diverse species, which like the Atlantic salmon (Salmo salar) and brown trout (Salmo trutta), has several forms or ecotypes differing in migrating behaviour. Several different forms distinct in morphology and nutrition behaviour may even inhabit the same water system. On the basis of migration behaviour, two common forms can be distinguished, the anadromous form, which migrates into the sea to feed and returns to fresh water to spawn and overwinter, and the land-locked form, which lives year round in fresh water. In Finland, the anadromous form occurs only in the Tenojoki (Tana), a river draining into the Barents Sea. In nutritionally poor environments, charr form dwarf populations. There are two different size forms in Finland, the small and the large charr, which at one time were considered two separate species. Nowadays only one Salvelinus species is considered to occur indigenously in Europe. Usually, in Finnish waters only one form occurs in one lake. The exception is Lake Inarijärvi, which is co-inhabited by both the small Arctic charr form, which feeds on bottom fauna and invertebrates, and the large predator form, which feeds on fish.

Reproduction: Like its relatives, the Atlantic salmon and the brown trout, the Arctic charr is an autumn spawning species, but unlike them, it releases eggs onto rocky bottoms, not in streams, usually at a depth of 1−5 m, in October or November. The bottom-feeding form in Lake Inarijärvi may even spawn at a depth of 15 m. Larvae hatch in the spring.

Large Arctic charr can weigh as much as several kilograms; the spawning size is usually 2−5 kg. In the Vuoksi catchment, Arctic charr females reach maturity at 5−6 years, when they are about 55−60 cm long and weigh a few kilograms. The small Arctic charr usually reaches maturity at a length of 30−35 cm and weight of 250-300 g. Some dwarf Arctic charr from mountain brooks mature when only about 8 cm long and weighing about 20 g.

Diet, growth and migrations: Arctic charr feed on zooplankton, surface insects, bottom fauna and fish. They vary greatly in growth rate and size from one catchment to another. Small Arctic charr grow slowly. In Lake Inarijärvi, for instance, 6-year-olds are less than 30 cm long, and in many mountain lakes growth is even slower. Large Arctic charr reach the legal catch size of 40 cm at 4 years of age in the Vuoksi catchment, and at a somewhat older age, 5−7 years, in Lake Inarijärvi. Most of Finland’s Arctic charr stocks are local. The only anadromous form occurs in the Tenojoki (Tana) catchment, where the smolts migrate to the sea at 3−5 years of age and return to the river only 2−3 months later.

Fishing and catches: In Northern Finland, the Arctic charr is significant for tourism and sport fishing. It is commonly caught with rod and lure, fly-fishing and, in winter, by ice fishing. In the mid-1970s the catch in Finnish Lapland was estimated to be about 13 000 kg, of which about 8 000 kg was caught in Lake Inarijärvi. In 2003, the catch of the lake, based on both releases and natural reproduction, was about 8 500 kg, whereas back in the 1930s before water level regulation for hydro-electric power started it was about 20 000 kg. The large Arctic charr in particular has suffered from the regulation of Lake Inarijärvi. The stock in the Vuoksi water system is too small to have any importance as catch fish.

Vulnerability, threats and management: Most charr stocks Arctic are near threatened (NT); in the Vuoksi catchment it is classified as critically endangered (CR). Threats to the original stocks come from fishing, water level regulation, releases of whitefish and acidification of waters. As a result of whitefish releases, Arctic charr has diminished in size, and the stock decreased. The Arctic charr is managed mainly by stocking, most commonly in Lapland and in North Karelia, eastern Finland. Tagging experiments show that stocking results have usually been poor, in the north mainly because of strong whitefish (Coregonus lavaretus) and/or abundant trout and pike (Esox lucius) stocks. Also, fishing for small charr has been too efficient. An effort has been made to protect the last indigenous stock, in Lake Kuolimo, in the Vuoksi catchment, by regulating fishing and raising the minimum legal catch size to 70 cm. Charr releases and the reconstruction of a reproductive stock can succeed only if gill-net fishing is restricted in the deeps of the open water area.

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