CHARACTERISTICS OF BUTYLTIN ACCUMULATION AND ITS BIOMAGNIFICATION IN STELLER SEA LION (EUMETOPIAS-JUBATUS)

The present study was conducted to examine sex difference, age, and te mporal trends of butyltin accumulation and its biomagnification in Ste ller sea lion (Eumetopias jubatus) collected from Alaska, USA, during 1976-1985 and from Hokkaido, Japan, during 1994-1995. Average concentr ation of total butyltin compounds (Sigma BTs) in the liver of Steller sea lion from Alaska (19 ng/g wet weight) was much lower than those fr om western and eastern Hokkaido, Japan (150 and 220 ng/g), respectivel y. This result suggests that Japanese coastal waters are contaminated with BTs in comparison with those of Alaska. In most samples, dibutylt in (DBT) residues were retained at higher levels than tributyltin (TBT ), suggesting the degradation of TBT to DBT in the liver. Sex differen ce and age-dependent accumulation of BTs residues were not found in St eller sea lion. Similarly, no prominent temporal trend in BT concentra tions was observed between 1976 and 1985. Nevertheless, the annual con sumption of organotin compound was doubled in the United States during the same period. These results suggest that the butyltin compounds ar e degraded faster than the intake from diet in Steller sea lion. The b iomagnification factor of BTs in Steller sea lion was low (0.15-4.6; m ean, 0.6), indicating that this animal is unlikely to magnify BTs due to rapid degradation and excretion.