Bioaccumulation of Mercury in Red Drum and King Mackerel: A Comparison of Total Mercury Concentrations in Two Gulf of Mexico Sportfish

The accumulation of mercury (Hg) in Gulf of Mexico (GOM) marine fishes such as King Mackerel (Scomberomorus cavalla) has been established; however, elevated Hg levels were only recently reported for Red Drum (Sciaenops ocellatus) and data are lacking from the central GOM. Our objectives were to 1) analyze total Hg concentration as a function of fish size and age, 2) investigate regional differences in these concentrations, and 3) compare total Hg concentrations in Red Drum to those in King Mackerel. We applied stable isotopic analyses of ¹³C and ¹⁵N to examine biomagnification of Hg based on trophic position and compared rates of bioaccumulation between both species. After accounting for the variance in mean total Hg due to size, there was no significant difference in total Hg concentrations between Red Drum and King Mackerel. Our results suggest that consumption of large Red Drum (> 660 mm total length) should be limited due to elevated total Hg concentrations (> 1ppm). In the GOM, harvest of large Red Drum is restricted (state waters) or banned (federal waters) in an effort to rebuild stocks. Our findings suggest this management measure may also protect the public from consumption of Red Drum with elevated Hg concentrations.