Ecological and biological factors associated to mercury accumulation in batoids (Chondrichthyes: Batoidea) from northeastern Brazil.

The present study aims to understand how ecological and biological factors affect the Hg levels in stingrays occurring in the Northeastern Brazilian coast. Total mercury (Hg), methylmercury (MeHg) and stable isotope (δ13C and δ15N) analyses were performed in five species. Hypanus americanus and Gymnura micrura showed the highest total Hg concentrations (300 and 176 ng.g-1, respectively). Hypanus guttatus exhibited a significant correlation between total Hg and size. Both species of the genus Hypanus presented the highest percentage of MeHg, around 100%, whereas the other species showed median percentages below 50%. The δ13C and δ15N signatures suggest that all studied species present the same foraging habitat but different trophic positions. Trophic position and animal size were the main factors influencing total Hg and MeHg concentrations in batoid species. The genus Hypanus, present in the Brazilian fish markets, showed concentrations above the accepted limits for human consumption.