Mercury concentrations in captive Atlantic bluefin tuna (Thunnus thynnus) farmed in the Adriatic Sea

Levels of total Hg in the muscle (29 samples) and liver tissues (15 samples) of bluefin tuna (Thunnus thynnus) weighing 100-300 kg were determined by cold vapour atomic absorption (AA) spectroscopy. Tunas were previously captured in the waters of Malta, towed to the farm in the Adriatic Sea and fattened with defrosted herring and sardine for the period of 6 to 7 months. The purpose of the investigation was to determine the magnitude of Hg contamination and to ascertain whether the concentrations in muscle tissue exceeded the maximum level defined by the European Commission Decision (1 microg/g wet weight). Total Hg concentrations in the muscles ranged from 0.49 to 1.809, while it was from 0.324 to 3.248 in the livers. Total Hg concentrations in six samples of sardine ranged from 0.050 to 0.072 microg/g wet weight, while two samples of herring contained 0.020 and 0.053 microg/g wet weight. Twelve out of 29 muscle samples of tuna contained Hg above the maximum level defined by the European Commission Decision.