Salt water-acclimated pink salmon fry (Oncorhynchus gorbuscha) develop stress-related visceral lesions after 10-day exposure to sublethal concentrations of the water-soluble fraction of North Slope crude oil.

Pink salmon fry. Oncorhynchus gorbuscha, after a 10-day exposure to one of two sublethal concentrations (25-54 microg x L(-1) or 178-348 microg x L(-1)) of the water-soluble fractions from Alaska North Slope crude oil, possessed morphologic and stress induced lesions in their hepatic, head kidney and gill tissues. Analysis of livers from oil-exposed fry revealed a variety of hepatocellular changes, including steatosis, nuclear pleomorphism. megalocytosis and necrosis. Epithelial proliferation of the bile ducts also occurred. An increase in the head kidney's interrenal cell nuclear diameter, a biomarker for stress responses, was correlated with hydrocarbon exposure. Gill abnormalities such as eqithelial lifting. fusion, mucous cell hyperplasia and vascular constriction were found in all test groups, but were more severe in fry given the high water soluble fraction of crude oil. The study demonstrated that sublethal exposure to the water-soluble fraction of crude oil results in multiple microscopic lesions (in several viscera) that are consistent with a pronounced response to environmental stress.