Geographic and ecological drivers of contaminants and nutrients in commercial fish species

Commercial marine fish are a major source of exposure to harmful compounds such as methylmercury (MeHg) but are also an important source of nutrients including selenium (Se) and omega-3 polyunsaturated fatty acids (ω-3). Safe eating guidelines seek to provide information to minimize the risk of contaminant exposure, while promoting the nutritional benefits of eating fish, yet information on the patterns and drivers of contaminants and nutrients are scarce, particularly within and across populations of commercially harvested marine fish species. This study assessed total mercury (Hg), Se and total lipids, along with subsets of MeHg and ω-3, in muscle tissue of six species of fish (Atlantic cod, Atlantic herring, red hake, silver hake, little skates and spiny dogfish) caught in the Gulf of Maine, the largest coastal fishery in the U.S. Fish species, as well as size and catch location (inshore vs. offshore) had a significant effect on concentrations of Hg and lipids, whereas Se concentrations varied little, except in skate. Higher length-adjusted concentrations of Hg and lower concentrations of lipids were found inshore for Atlantic cod, whereas the reverse was true for Atlantic herring, and Hg was also higher in offshore spiny dogfish. Stable isotope analysis and differences in catch timing suggest these patterns are due to seasonal and locational differences in plankton community compositions and in prey availability to pelagic and demersal fish. These findings reveal that local environment plays an important role in determining both nutrient and contaminant load, and points to the effects of environmental change on the risk-inducing and beneficial qualities of commercially caught fish.