Metals and other elements in tissues of wild fish from fish farms and comparison with farmed species in sites with oxic and anoxic sediments.

Farmed fish and wild fish aggregating in the vicinity of four Mediterranean fish farms with different environmental conditions were sampled. Levels of metals (including As and Se) were measured in the muscle, liver, gills, bone and intestine. The wild fish from sites with anoxic substrata accumulate metals (including As and Se) from the ambient habitat in their gills whereas those from sites with oxic substrata concentrate these elements through their diet in their intestine. Tissues of wild fish aggregating around farm cages accumulate a greater number of these elements and with higher concentrations than farmed fish. Habitat, diet, ecological needs, fat content of fish, and protein expression may play an important role in these element differences between fish species. Fe in flathead grey mullet, As in surmullet, rainbow wrasse, grey gurnard and picarel and Hg in bogue may pose a risk for human health. Farmed and wild fish are good sources of P, K, Cr and Se while flathead grey mullet, picarel and comber are excellent sources of Ca and Se.