Total mercury concentrations in sand flathead, Platycephalus bassensis Cuvier & Valenciennes, from Port Phillip Bay, Victoria

Abstract

Total mercury concentrations were measured in the axial muscle tissues of 562 sand flathead (Platycephalus bassensis) from a total of 37 sites within Port Phillip Bay, Victoria. Mean concentrations of mercury (0.23 ±0.18µg g^-1 wet weight) were less than half (P<0.05) of those recorded for this species during 1975-78 and below the Victorian health standard for fish and fish products (i.e. less than a mean concentration of 0.5 µg g^-1 wet weight) at all 37 sites. During the 1975-78 period, mercury concentrations in sand flathead from the bay were reported to decrease from north to south and from east to west. During 1990, however, mercury concentrations were found to be related to the water depth at which the fish were sampled. Sand flathead from the deeper (22 m) waters of the bay had significantly (P<0.05) higher mean mercury concentrations than did those collected from shallower (7 m) waters. The overall mean mercury concentration in sand flathead from the bay during 1990 approached the mean concentration in sand flathead collected from six sites in Bass Strait (0.22 µg g^-1) during 1975-78, although the range of concentrations for the Port Phillip Bay samples (0.01- 0.89 µg g^-1) was wider than that for the Bass Strait samples (0.1-0.33 µg g^-1).