Heavy Metal Food Chain: Relating Feeding Ecology and Mercury Bioaccumulation in Southern New England\u27s Top pelagic Predators

Mercury accumulation of upper trophic level marine fishes is a growing concern for human consumers. Diet is the primary source of mercury bioaccumulation in both fish and humans and yet remains unexamined in many intensely fished regions such as southern New England (SNE). The feeding ecology and mercury concentrations of recreationally caught albacore (Thunnus alalunga) and yellowfin (T. albacares) tunas, shortfin mako (Isurus oxyrinchus) and common thresher (Alopias vulpinus) sharks and dolphinfish (Coryphaena hippurus) were evaluated. Important prey were identified and also measured for total mercury content. Seventy percent of the predator fishes sampled in this study had mercury concentrations greater than the EPA recommended 0.3ppm, and included shortfin makos (2.65 ± 1.16ppm), threshers (0.87 ± 0.71ppm) and albacore (0.45 ± 0.14ppm). Mercury concentrations were lowest in dolphinfish (0.20 ± 0.17ppm) and yellowfin (0.32 ± 0.09ppm). Length was positively correlated with mercury content and bioaccumulation rates were linear for tunas and dolphinfish, while exponential for both shark species. Small schooling fishes (Pomatomus saltatrix, 0.110 ± 0.102ppm) were the primary prey of shortfin makos. Shortfin squid (Illex illecebrosus, 0.028 ± 0.005ppm) was a principal and consistent dietary component of both tunas and dolphinfish diets. The diets of SNE dolphinfish and yellowfin tuna were more invertebrate dominated than other regions previously examined. Though the method of sample collection for this study biases toward larger individuals, these are the sizes of fish targeted by anglers, generally for human consumption