TOTAL MERCURY CONCENTRATIONS IN SAND FLATHEAD, PLATYCEPHALUS-BASSENSIS CUVIER AND VALENCIENNES, FROM PORT-PHILLIP BAY, VICTORIA

Total mercury concentrations were measured in the axial muscle tissues of 562 sand flathead (Platycephalus bassensis) from a total of 37 sit es within Port Phillip Bay, Victoria. Mean concentrations of mercury ( 0.23+/-0.18 mug g-1 wet weight) were less than half (P<0.05) of those recorded for this species during 1975-78 and below the Victorian healt h standard for fish and fish products (i.e. less than a mean concentra tion of 0.5 mug g-1 wet weight) at all 37 sites. During the 1975-78 pe riod, mercury concentrations in sand flathead from the bay were report ed 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 d uring 1990 approached the mean concentration in sand flathead collecte d from six sites in Bass Strait (0.22 mug g-1) during 1975-78, althoug h the range of concentrations for the Port Phillip Bay samples (0.01-0 .89 mug g-1) was wider than that for the Bass Strait samples (0.1-0.33 mug g-1).