Effects of species, sex, length and locality on the mercury content of school shark Galeorhinus australis (Macleay) and gummy shark Mustelus antarcticus Guenther from south-eastern Australian waters

Abstract

The mercury levels detected in the muscle tissues of sharks ranged from 0.01 to 2.7 pprn wet weight for school shark Galeorhinus australis (Macleay) and from 0.07 to 3.0 ppm for gummy shark Mustelus antarcticus Guenther. Estimates of the mean mercury levels for the 1971 Victorian landed commercial shark catch were found to be 0.90 ppm for the school shark and 0.37 ppm for the gummy shark. The analyses for total mercury determinations were carried out by five independent laboratories. Preliminary analyses carried out by one indicatcd that most of the mercury in school sharks and about two-thirds of the mercury in gummy sharks was present as methylmercury. The mercury concentrations varied exponentially with shark length. School sharks had statistically significantly higher mercury levels than gummy sharks of the same length and for both the medium- sized and large individuals of each species males had significantly higher levels than females. Levels in male gummy sharks were found to be affected by locality.