Koroleva I.M. The status of whitefish population from Chuna Lake in the Lapland Biosphere Reserve Russia. International Journal of Environmental Research. 2008, V.2, №2, p. 111-124.

Int. J. Environ. Res., 2(2): 111-124, Spring 2008 1800 1500 Э 1200 й 900 W 600 300 0 LL trout pike perch burbot □ 1949 □ 2000-2001 70 60 a 50c Л 4 0 Iff 30 ^ 20 10 0 trout pike perch burbot □ 1949 □ 2000-2001 Fig. 6. The average size-and-weight indices of fish in Lake Chuna, according to the earlier studies (Vladimirskaya, 1951) and own data (2000-2001) Skin coverings _ coloration I changes Changes of gills Changes of liver Changes of kidney 0 10 20 30 40 50 60 70 80 90 Frequency of pathology occurrence (%) Fig. 7. Frequency of occurrence of pathological changes of whitefish in the Lake Chuna in the catches of 2000-2001 It is known that fish can avoid unfavorable environment, including the areas with high concentrations of pollutants. Among the fish studied, there were some individuals with abnormally high copper concentrations in all organs. This phenomenon was recorded throughout the whole study period, being particularly typical for autumn - winter period (Fig. 8, 9). The reason for this may be high level of metal input into the organismwith food in summer, which is a feeding period, and, on the whole, a higher exchange level. With the feeding rate decreasing in winter, excessive toxicants can be removed from organism by biochemical processes. Metals are known to be primarily absorbed by mucus membranes (gills, digestive tract and skin). Then these are transported from gills and digestive tract into blood to be distributed in various parts of the body. Muscles, as a rule, accumulate Cu and Ni in fewer quantities. Liver is an organ with a higher copper accumulative capacity, kidneys accumulate nickel (Bradley and Morris 1986; Graehl et al., 1985), which is confirmed by the present study. Variation and high concentrations of heavy metals in organs and tissues ofwhitefish in autumn may be caused by cyclic change in temperature conditions in the water body. The precipitation is known to increase in autumn, which is followed by more intensive outwashing of pollutants from the atmosphere and the catchment area. Analogous but more intensive process is also pollutants intake into water bodies in spring snowmelt. Of great danger is the increase in water acidity, which is able to stimulate partial heavy- metal release from bottom sediments and increase their mobility. Of significance is also the fact that whitefish under study have a benthic type of nutrition. An increase in water temperature in summer can also affect the fish because, as the temperature rises the metal activity and mobility rise sharply. Besides, the increase o f water temperature results in intense gill ventilation, due to increased oxygen need, related to metabolic needs and/or decrease of oxygen concentrations in water (Douben, 1989; Heath, 1987). In the period o f stable ice cover, low oxygen concentrations in water stimulate intensive resp iration , which may increase metal concentrations in gills. Alongside with it, in case of low oxygen content in near-bottom layers, it is possible for heavy metal to partially release from bottom sediments (Dauvalter, 1998). A comparative analysis of Cu and Ni concentrations in organisms of brown trout (predator, inhabits 119