Effect of Trawling and Habitat on Mercury Concentration in Juvenile Red Snapper from the Northern Gulf of Mexico

Abstract

We evaluated mercury (Hg) contamination in juvenile red snapper Lutjanus campechanus (<250 mm total length) as an indicator of Hg pollution on the northern Gulf of Mexico (GOM) continental shelf. Specifically, we examined the effects of fish size, commercial shrimp trawling, and habitat type on total Hg concentrations and stable nitrogen isotope ratios (δ¹⁵N; a proxy for trophic position) in red snapper. Red snapper Hg concentrations and δ¹⁵N values were positively and significantly correlated with fish size. In addition, red snapper collected over trawled habitats had significantly higher Hg concentrations and δ¹⁵N values than did red snapper collected from similar, nontrawled habitats. Red snapper also exhibited habitat-specific differences in Hg concentrations and δ¹⁵N values, but differences were size dependent and generally small. Our study suggests that the Hg concentrations of juvenile red snapper in the northern GOM are elevated in areas where commercial shrimp trawling occurs, possibly due to increases in both red snapper trophic position and bioavailable Hg in trawled areas. Additional studies are needed to determine whether Hg concentrations are elevated in fish from trawled areas in other marine ecosystems.