HEAVY-METALS IN TISSUES OF FISH OF THE PSKOVSKO-CHUDSKOYE AND VIRTSYARV LAKES

By the atomic adsorption methods, contents of cadmium, lead, copper, zinc and iron were determined in muscles, gills and liver of 7 fish species differing in their environment and nutrition type, It has been found that in tissues of fishes inhabiting a deeper and larger basin - the Pskovsko-Chudskoye lake, which is under a strong anthropogenic pressing, the contents of heavy metals is the same as in fishes of a much smaller and more shallow Virts'yarv take known to be free from industrial sewage. The order of increasing metal contents in tissues of fishes is the following: cadmium, lead, copper, zinc, iron. Irrespective of fish species, the highest metal content was in the liver, while the lowest in muscles, the ionic content of metals in the latter never exceeding the admitted level. In both the lakes the bentosphages, compared with fishes of mixed nutritioned type and predators, accumulated more cadmium and zinc, whereas the predators accumulated more copper and iron in their tissues compared to fishes of other nutritional types.