GEOGRAPHICAL-DISTRIBUTION AND ACCUMULATION FEATURES OF ORGANOCHLORINE RESIDUES IN FISH IN TROPICAL ASIA AND OCEANIA

Concentrations of persistent organochlorine residues were determined in fish collected from several locations in eastern and southern Asia and Oceania to identify the accumulation features of such residues in tropical aquatic organisms and to elucidate their distribution in tropical developing countries. DDT and its derivatives (DDTs) were the predominantly identified compounds in most locations. In general, the concentrations of organochlorines in tropical fish were lower than those in fish of the temperate regions. Residue levels in fish showed little spatial variability, as reported for tropical sediments. This is different from the patterns observed for air and water in which higher concentrations occur in tropical latitudes compared to mid-latitudes. Compilation of limited available data on the organochlorine residue levels in fish in tropical Asian countries seemed to indicate little temporal variability due to the low levels of accumulation in aquatic organisms, despite the continuous use of these compounds. A short residence time of semivolatile organochlorines in the tropical aquatic environment results in lower levels of accumulation of residues in fish. Examination of walleye pollock (Theragra chalcogramma) collected from the Bering Sea indicated that organochlorine residue levels are declining in temperate water bodies near the Arctic Ocean in recent years.