Mercury content of tropical sharks
Department of Industry Tourism and Trade
1. Sample up to 1000 sharks of various spp for total mercury content; determine alkyl mercury levels in approximately 150.
2. Examine effects of sex, length, locality on levels. What implications for future of this shark fishery?
3. Sample up to 200 sharks for selenium content
Total mercury, alkyl mercury and selenium concentrations in the muscle tissue of several species of pelagic sharks from northern Australian waters are reported. Mean mercury concentrations ranged between O .13 mg /kg for Carcharhinus brevipinna and 1. 94 mg/kg for C. amblyrhyn choides. Maximum values exceeded 1.5 mg/kg in nine of the species studied and the highest recorded concentration was 3.7 mg/kg for Sphyrna mokarran.
Mercury concentrations were highly dependent on the size of shark, a relationship that was adequately represented by the power function. Males of most of the species studied had significantly higher levels of mercury than females of similar size.