Implications of age, size and region on mercury contamination in estuarine fish species

This study investigated the effects of age and length on mercury contamination in four fish species; yellow-eye mullet (Aldrichetta forsteri),black bream (Acanthopagrus butcheri), sand flathead(Platycephalus bassensis) and sea-run brown trout(Salmo trutta) from the Derwent Estuary, Tasmania,Australia, and examined the implications of these findings for public health monitoring. Mean mercury levels exceeded the Food Standards Australia and New Zealand maximum permitted level (0.5 mg kg−1)for all species except yellow-eye mullet. Mean levels in black bream were significantly higher (p<0.05)than other species and consequently are a particular concern for human health. Regional differences (p< 0.05) in mercury levels in sand flathead were not obviously correlated with metal levels in the sediments. However, age and length significantly (p<0.05) influenced mercury levels in brown trout and sand flathead, with age being more strongly related to intraspecies differences. In addition, movement and distribution within the estuary and trophic status appeared to be important factors in contribution to interspecific variation. Consequently, a sound understanding of fish life history and biology is important in identifying species which may be susceptible to accumulating mercury and hence pose a potential threat to human health.