DID NATURAL CHANGES SAVE THE GREY SEAL OF THE BALTIC SEA? HYPOTHESIS OR REALITY

摘要

The concentrations for two most important PCB isomers l UPAC. l 38 and l 53 in the blubber of 2 6 year old grey seals varied from 2.3 4. l mg/kg (extractahlr fat) and from 2.9 5.2 mg/g (extractablr fat) respectively. Compared to the end of l970s and the beginning of l980s. at least the PCB concentrations obtained by food in grey seals in West-Estonian Archipelago Reserve must have decreased. This is probably the result of natural changes in last twenty years (decrease in salinity and oxygen concentration in the Gotland Deep). Comparing the food chain of grey seal in the coastal waters of Estonia at thc beginning of l970s and species content during experimental catches in spring l994, we can assume that nowadays the grey seals do not eat so much cod, salmon and sea t rout as in thc end of 1 970 and in the beginning and in the middle of 1980s.