Trace metal incorporation in otoliths of black bream (Acanthopagrus butcheri munro), an indicator of exposure to metal contamination

Otoliths of black bream (Acanthopagrus butcheri) collected from the Swan River Estuary were analysed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to measure concentrations of 14 trace metals. Trace metal concentrations in the otoliths may be related to the environmental exposure history of fish to contamination. The following metal isotopes were investigated: aluminium (Al-27), calcium (Ca-44), manganese (Mn-55), iron (Fe-57), copper (Cu-65), zinc (Zn-66), strontium (Sr-88), cadmium (Cd-111), tin (Sn-120), barium (Ba-138), mercury (Hg-202), lead (Pb-208) and the metalloids arsenic (As-75, As-77) and selenium (Se-82). Significant differences in otolith trace metal composition were found between sampling sites. Lead and Fe-57 were consistently lower in downstream fish relative to upstream fish, while Sr-88 varied with the salinity gradient in the urban estuary. Lead and Fe-57 followed similar patterns within the otoliths, and appeared to provide the best discriminatory power for relating otolith metal concentration to the environmental history of the fish.