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

Lake Layer, cm LOI Cu Ni Zn Co Cd Pb As Hg cd Kochejaur 0-1 51.96 16 25 84 10.3 0.62 25.4 2.60 0.016 18-19 41.44 16 20 69 8.8 0.16 1.8 1.13 0.012 c, 1.0 1.3 1.2 1.2 3.9 14.1 2.3 1.4 26.3 1.16.3. Hydrobiological studies Ichthyofauna. Studies on the fish community of Lake Kochejaur were conducted in 1990-1992, and in 2002 and 2005. The Ichthyofauna of the lake consists of eight species belonging to eight fish fami­ lies: trout ( Salmo trutta ), whitefish ( C oregonu s lavaretus), grayling ( Thumallus Thu­ mallus), pike (Esoxlucius), perch ( Perea fluviatilis), burbot ( Lota lota), minnow ( Phox­ inus phoxinus ), and nine-spine stickleback ( Pungitius pungitius). Overall, whitefish and perch are the dominant species in Lake Kochejaur (Fig.14). Pike, trout, grayling and burbot occur in isolated parts of the lake, and minnow and nine-spine stickleback in the littoral parts of the lake. Sparsely rakered whitefish are present in the lake (up to 30 gill rakers). The mean length varies from 24.5 to 29.6 cm, and mean weight from 258 to 323 g (Fig. 15). The maximum length can reach 56.5 cm and weight 2575 g. Fish with a weight up to 400 g and length 25-30 cm are the most numerous (Fig. 15). The age limit ofwhitefish is 17+, al­ though specimens ofyounger age groups (1+) and specimens older than 10 years are occasionally caught (Fig. 16). The reason for the absence of young fish is the silting up of the water body and a lack of spawning areas. At the same time the lake provides favourable conditions for fish feed­ ing. This is the reason for the feeding migration of whitefish from other water bodies trout 0.5 perch 36.8 Я pike 2.4 whitefish 60.4 Table 16. The organic matter con­ tents (LOI, %) and heavy metal concentrations (цд/д, dry weight) in the surface (0-1 cm) and pre-industrial (18-19 cm) sediment layers. Cfand Cd are contamination factor and degree of contami­ nation values, respec­ tively. Fig. 13. Vertical distribution of the concentrations of Cd and Pb (цд/д, dry weight) in sediments from the northern, central and southern parts of Lake Kochejaur. Fig. 14. Distribution of fish spe­ cies in Lake Kochejaur Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea 51