Peled whitefish

(Coregonus peled)

Order: Salmoniformes Family: Salmonidae Subfamily: Coregoninae

Foto: Lauri Urho

Description: A whitefish resembling, bright shoal fish with an adipose fin, the peled whitefish thrives in open water areas. Unlike the whitefish (Coregonus lavaretus), but similarly to the vendace (Coregonus albula), the lower jaw of the peled whitefish is a little longer than the upper jaw. Also its body shape is higher. The gill arches have dense and long gill-rakers, usually numbering from 50 to 65. Its preferred habitats are in open water areas.

Origin and distribution: The peled whitefish is indigenous to Russia, to the area between the River Mezen, which drains into the White Sea, and the Kolyma in eastern Siberia. Several different ecological forms occur in Siberia, and today the peled whitefish has been introduced into many parts of Europe. As well as Finland, it occurs in the Baltic countries, in western Russia and in Poland. The first peled whitefish eggs were brought to Finland from a hatchery near St. Petersburg in 1965, the aim being to find a fish species that would thrive in altered water systems and would increase their value for fishing and fish production. In the 1960s and 1970s, peled whitefish were released into several lakes. The best result was achieved in the Lokka and Porttipahta reservoirs, in which even natural reproduction was observed in the late 1980s. In addition to the upper reaches of the Kemijoki, the species has been introduced into some small lakes in southern Finland.

Reproduction: Peled whitefish reach maturity at about 3 years of age. The spawning time varies in different parts of the range. In the reservoirs, spawning usually takes place under the ice in November or December, at a depth of 2−3 m, on a sand or gravel bottom. The larvae hatch at a length of 8−9 mm after the ice cover has melted.

Diet, growth and migrations: Peled whitefish filter zooplankton, mainly cladocers and copepods for food. Like vendace, they swim near the surface in both coastal and open waters during their growth period. Despite the short growing period in the north, peled whitefish grew well in the 1980s, attaining a weight of 0.5 kg in three growth seasons. In the reservoirs, a couple of large age-groups were born naturally in the late 1980s–early 1990s, resulting in a multiple increase in the size of the stock but a decrease in the growth rate of the fish. Three- to four-year-olds, which had previously weighed 500 g, now weighed only 150 g. Since then, however, the stock size has decreased and the growth rate has improved.

Fishing and catches: During spawning time, peled whitefish gather into shoals, and drift-net catches under the ice are at their largest. When the size of fish decreased, net fishing was replaced by trap-net and trawl fishing, which increased catch sizes dramatically. In 1992−1994, peled whitefish catches peaked at 300 tonnes from the two large reservoirs. When natural reproduction ceased, catch sizes declined and in 1999, for instance, the catch from the reservoirs was only about 4 tonnes.

Vulnerability, threats and management: As natural reproduction of the species is only occasional or, at least, extremely variable, maintenance of peled whitefish stocks requires continuous releases. When natural reproduction succeeds, fisheries management is all important. Laid eggs are often destroyed by regulation of the water level of lakes in winter and a lack of oxygen. Interest in the species has diminished somewhat in recent years.

Text version