Risk-benefit analysis of fish consumption: Fatty acid and mercury composition of farmed southern bluefin tuna, Thunnus maccoyii

The docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) contents and total mercury concentration were measured in whole tissue composites of all edible tissues of wild caught and farmed southern bluefin tuna (Thunnus maccoyii, SBT) and each of the marketed tissue cuts (akami, chu-toro and o-toro) of these fish. Rapid lipid accumulation during culture resulted in a net reduction in mercury concentration of SBT composite tissues and an increase in the concentration of the dietary essential fatty acids. Moreover, the increased affinity of lipid for certain tissue cuts (o-toro) over that of others (e.g. akami), resulted in cross carcass variation in the mercury concentration of fish muscular tissue. Results highlight the potential for farming to be used as a tool to improve the flesh quality of fish species which could otherwise provide limited dietary essential fatty acids to consumers and potentially contain elevated contaminant levels.

► Farming of wild caught SBT enhanced the total lipid content of fish tissues.
► Lipids in farmed SBT had a higher proportion of EPA and DHA than lipid in wild caught SBT.
► Tissues of farmed SBT with higher lipid content were also found to have a higher proportion of EPA and DHA.
► Farming improved the flesh quality of SBT by increasing EPA and DHA content and decreasing mercury concentration.