Mercury and Organochlorines in Black Bream, Acanthopagrus butcheri, from the Gippsland Lakes, Victoria, Australia: Evidence for Temporal Increases in Mercury levels

Total mercury and organochlorine insecticide (α-HCH, lindane, β-HCH, heptachlor, δ-HCH, aldrin, heptachlor epoxide, α- and β-endosulfan, dieldrin, 4,4′–DDE, endrin, 4,4′-DDD, 4,4′-DDT) concentrations were measured in black bream from 10 widely separated sites within the estuarine Gippsland Lakes, Victoria south-east Australia. Mercury concentrations (mean 0.22 μg g−1 wet weight) in the axial muscle tissues were below the maximum concentration in fish permitted for human consumption (0.5 μg g−1), but they were at least 58% higher than those for black bream tested during 1978–79. The cause of the observed increase was not investigated in this study. However, while most of the mercury in the Gippsland Lakes catchment is thought to be due to the legacy of past gold mining, atmospheric emissions from coal burning power plants are likely to contribute to the existing load. Organochlorine insecticides were detected in all fish, but the concentrations were <10 ng g−1 (wet weight) in both axial muscle and liver tissues. These levels are at least one order of magnitude below the maximum residue levels permitted in fish for human consumption. The bis-chlorophenol (DDT) group of insecticides was the major component in most cases, and lipid weight concentrations varied between 12 and 85 ng g−1 (mean 39 ng g−1) for axial muscle tissues and between 17 and 61 ng g−1 (mean 35 ng g−1) for liver tissues.