Levels of mercury and organohalogen compounds in Pacific bluefin tuna (Thunnus orientalis) cultured in different regions of Japan.

Contamination levels of total mercury (T-Hg), p,p'-DDE, and polychlorinated biphenyls (PCBs) in akami (leaner meat) and toro (fatty meat) samples from Pacific bluefin tuna cultured in the southern (four locations) and central (three locations) regions of Japan were analyzed. The contamination level of T-Hg in the akami and toro samples from the southern region tended to decrease with an increase in latitude, whereas those of p,p'-DDE and PCBs tended to increase. These spatial trends in contaminants were similar to those reported previously in wild tuna caught off the coast of Japan (Hisamichi et al., in Environ Sci Technol 44:5971-5978, 2010). However, the contamination level of T-Hg in akami and toro samples from one location in the central region was the highest among all seven locations, whereas the contamination level of p,p'-DDE was lower than that from any location studied in the southern region. Thus, contamination levels of T-Hg, p,p'-DDE, and PCBs in the cultured tuna may reflect contamination levels not only in the marine environment but also in prey fish used as bait.