Organochlorine residues in Dall's and True's porpoises collected from North-western Pacific and adjacent waters

The levels of organochlorine residues (PCB and p, p′-DDE) in the adult male Dalli and Truei porpoises collected from North Pacific, Bering Sea and Japan Sea are reported. Different levels of these compounds were observed in the individuals with respect to sex and location, indicating the fact that man-made organics can be used as chemical indicators in tracing out certain ecological and physiological events in long-life marine animals. Considerably lower levels of these chemicals were detected in the blubber samples of adult females when compared with the adult males from the same area, indicating parturition and lactation as the possible major routes of excretion in females. On the basis of different ranges and means of PCB and DDE concentrations, certain suggestions are also made about the different feeding grounds and the geographical ranges of Dall's and True's porpoises in the present study area.