On mercury and selenium in tuna fish tissues. IX. The levels of mercury and selenium in gonad of yellow fin and albacore

The levels of mercury and selenium in twenty-eight gonad specimens of two species of tunas, i.e., sixteen individuals of yellow fin Thuunus albacares and twelve individuals of albacore Thunnus alalunga, are presented. Total mercury content (T-Hg) correlated significantly between gonad and muscle, and T-Hg in gonad was about 30% of that in the muscle. The ratio of methyl mercury content (MeHg) to T-Hg in gonad was small compared with that in the muscle. Selenium content (Se) was relatively high, and Se in yellow fin was significantly high compared with that in albacore. Moreover, in both the species, Se in the ovary was significantly high com-pared with that in the testis. The molar ratio (Se/Hg) of Se to T-Hg correlated negatively with T-Hg, and tended to get nearer to 1 with the increase in T-Hg.