Comparison of stable isotope composition and inorganic and organic contaminant levels in wild and farmed bluefin tuna, Thunnus thynnus, in the Mediterranean Sea

Stable isotope composition (d13C and d15N) and persistent pollutants, including heavy metals (Hg, Cd, Pb,As, Cu, Zn) and organochlorine compounds (PCBs, HCB and p,p0-DDE), were measured in muscle and livertissues of wild and farmed bluefin tunas to investigate the changes occurring during the farming periodand to assess the quality, in terms of contaminants, of the final product. At the end of farming, the foodsupplied was clearly integrated into the tuna tissues as derived from stable isotope signatures, and,contrarily to the literature findings obtained for other species, farmed tunas showed slight variationsin persistent elements and chemical compounds in comparison with wild fish. The low tissue turnoverof long-lived adult tunas together with the short farming period appeared to act to preserve the initiallow contamination levels in the absence of new, elevated contamination sources (feed and environment),determining an acceptable quality of the final aquaculture product.