BIOACCUMULATION OF CHLOROHYDROCARBON PESTICIDES BY FISH IN THE NATURAL-ENVIRONMENT

Examination of chlorohydrocarbon pesticide data in fish from rivers on the North Coast of New South Wales, Australia suggests that exposure to upstream waters contaminated with dieldrin and DDT and metabolites leads to increasing residues of these substances with age. However, movement to clean oceanic and estuarine waters during the spawning migration downstream by adults results in depuration and lowering of the pesticide residues. This finding was supported by continuing increased residue levels in non-migrating fish throughout their life cycle. The chlorohydrocarbon concentration in the fish was also used to estimate overall pesticide concentrations in the water of the rivers using the bioconcentration factor for fish calculated from the octanol/water partition coefficient. Analysis of the data suggests variations in residue levels observed with different geography and species were due principally to variations in the fat content and different exposure histories of the fish.