| Abstract
| - Concentrations of butyltins (BTs) in the liver andorganochlorine compounds (OCs) in the blubber ofRisso's dolphins collected off Taiji, Japan, in 1991 weredetermined. Mean and range concentrations (wetweight basis) of these compounds were 3.6 μg/g (0.55−6.0 μg/g) for BTs, 25 μg/g (1.7−120 μg/g) for PCBs,17 μg/g (0.45−77 μg/g) for DDTs, 4.0 μg/g(0.19−16μg/g) for CHLs, and 0.16 μg/g (0.008−0.74 μg/g)forHCHs. OCs concentrations increased with age in malesin contrast to that in females, which showed adecreasing trend after maturity. On the other hand,no difference was observed in BT concentrationsbetween male and female, which showed increasinglevels until maturity (8−10 years) and then remainedconstant. It is suggested that, unlike OCs, BTs wereless transferable to young ones in reproductiveprocesses. Risso's dolphins showed higher biomagnification factor (about 6) than Steller sea lion (0.6),implying a slower excretion rate of BTs in cetaceansthan in pinnipeds due to the lower degradationcapacity of xenobiotics and the lack of physiologicalprocesses such as shedding of hair in cetaceans.
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