Sandimirov S.S. Catalogue of lakes in the Russian, Finnish and Norwegian Border Area. Finland, Jyvaskyla: Kopijyva Oy, 2008.

Hydrobiological studies H yd rob iologica l in d ices The phytoplankton communities in the lakes consist of cyanobacteria, diatoms, yellow- green algae and green algae. Cladocerae and Copepoda form the dominant zooplankton communities. The predominant species in the benthic communities are Chironomids, mayfly ( Ephem eroptera) and stoneflies ( P lecop tera ). Despite the extremely high level of pollution, Lake Kuetsjarvi is the richest lake as regards the number of zooplankton species, and also has considerable species diversity in bottom organisms. The number of zoobenthos species is over 20, with Chironomids predominating (60-80%). Ichthyofauna According to the studies on fish communities in the Finnish, Norwegian and Russian border area, the ichtyofauna of the lakes comprises 14 fish species. The most common species are whitefish, perch and pike. The whitefish in forest lakes (Aittojarvi, Kanto­ jarvi, Suovaselkajarvi, Mellalompola, Kochejaur, and Virtuoshjaur) were represented by the sparsely rakered form only. Whitefish. The densely rakered whitefish was caught only in Lake Kuetsjarvi. The sparsely rakered whitefish in this lake had the smallest length and weight. The largest whitefish occurred in lakes Suovaselkajarvi and Kochejaur (Fig. 81). The whitefish in Lake Stuorajavre also had high lengths and weights. The maximum age of the white- fish varied within broad limits.The maximum whitefish age was in Lake Kochejaur (18 years). Overall, the maximum age of whitefish in the small forest lakes in the region varied from 4+ (Suovaselkajarvi) to 11+ (Kochejaur). Normally, whitefish reach maturity at the age of 5-8 years (Reshetnikov, 1980). However, as a result of long-term exposure to pollutants, the whitefish in some lakes reached maturity at the extremely early age of 0+-1+ and had a minimum weight of 6-14 g and length 8.9-12.1 cm (Lake Kuetsjarvi). The whitefish in Lake Stuorajavre reached maturity at the age of 5 years. Whitefish spawning for the first time at the age of 3 years were found in water bodies (Kochejaur, Virtuovoshjaur) located at consider­ able distances from the emission sources. Catalogue o fLakes in the Russian, Finnish and Norwegian BorderArea 137