Effects of freshwater exposure to arsenic trioxide on the parr-smolt transformation of coho salmon (Oncorhynchus kisutch)

The effects of chronic (6 months) exposure to arsenic trioxide in fresh water on the Parr-smolt transformation of coho salmon (Oncorhynchus kisutch) were evaluated. Exposure to 300 μg As/L (as As₂O₃) appeared to delay the onset of the normal increase in plasma thyroxine concentration and cause a transient reduction of gill Na⁺,K⁺-ATPase activity. Fish exposed to 300 μg As/L also migrated to the sea less successfully than did nonexposed smolts, but there were no effects on the survival and growth of smolts held in 28‰ salt water for 6 months.