Levels of polychlorinated biphenyls (PCB) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in fillets of farmed Southern Bluefin Tuna (Thunnus maccoyii)

Southern Bluefin Tuna (SBT) (Thunnus maccoyii) is the only farmed tuna species in the southern hemisphere, with production centred offshore of Port Lincoln, South Australia. SBT farming is a quota-based fishery where farmers fatten wild-caught stock for subsequent sale as fresh-chilled or frozen product, mainly to Japanese markets. Fillets from wild-caught and farmed SBT were analysed and the concentration of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are reported for the first time. Time of farming was separated into two periods: a typical farming period of approximately five months and an experimental scenario that involved holding (farming) these fish for an additional 12 months. WHO-PCB and WHO-PCDD/F TEQ concentrations in fillets on a fresh weight basis at the same times and over the same periods were, 0.67-1.18pg-TEQg(-1) and 0.16-0.29pg-TEQg(-1), respectively. All WHO-PCB congeners, and only three WHO-PCDD/F congeners, were found to biomagnify during farming, after blank correction. Caution should be exercised when extrapolating these results to SBT farming as a whole because of the use of varying husbandry and feeding practices employed by different companies.