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

Table 37. The organic matter contents (LOI, %) and heavy metal concentra­ tions (цд/д, dry weight) in the surface (0-1 cm) and pre-industrial (24-25 cm) sediment layers. Cfand Cdare con­ tamination factor and degree ofcontamination values, respectively. Fig. 50. Vertical distribution of the concentrations ofPb, As, Cd and Hg (pg/g, dry weight) in the sediment core of Lake Stuoraja- vre-1. Fig. 51. Distribution offish spe­ cies in Lake Stuorajavre. maximum Hg in the 2-3 cm layer (Fig. 50). The contamination factor values for these heavy metals range from 1.5 to 2.4 (Table 37), i.e. the values correspond to moderate contamination. Lead has the highest Cfvalue. The contamination factor values for the other heavy metals are low. The degree of contamination value (11.5) for this lake cor­ responds to moderate contamination. Lake Layer, cm LOI Cu Ni Zn Co Cd Pb As НЯ C h Stuorajavre-1 0-1 16.79 48 45 55 38.1 0.21 10.9 4.41 0.126 24-25 12.32 73 43 51 34.8 0.14 4.4 3.14 0.055 c, 0.7 1.0 1.1 1.1 1.5 2.4 1.4 2.3 11.5 2.13.3. Hydrobiological studies Ichthyofauna. The studies on the fish community of Lake Stuorajavre were conducted in 2005. The ichthyofauna of the lake consists of nine species belonging to eight fish families: trout (Salmo trutta), arctic char ( Salvelinus alpinus ), whitefish ( C ore­ g o n u s lavaretus), grayling ( Thumallus thumallus ), pike ( Esox lucius), perch ( Perea Huviatilis), burbot ( Lota lota), minnow ( Phoxinus phoxinus ) and nine- spine stickleback ( Pungitius pungitius). Overall whitefish and perch are the predominant species in Lake Stuorajavre (Fig. 51). Pike, trout, grayling and burbot are occasionally caught. Two forms of whitefish inhabit the lake: sparsely rakered whitefish (up to 30 gill rakers) and densely rakered whitefish (30 to 40 gill rakers). The mean length and weight of the densely rakered whitefish do not exceed 23.7 cm and 145 g, respectively. The largest individuals can reach 27.2 cm and 220 g. The bulk of the densely rakered whitefish population is represented by fish with a length of22-26 cm and weight 140- 160 g (Fig. 52). On the average, the sparsely rakered whitefish are slightly larger than 104 Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea