Evaluations of the effects of petroleum on the indigenous marine fauna of Alaska's continental shelf regions are of continuing importance because of existing and proposed oil exploration activities in these areas. The purpose of the present study was to determine the influence of crude oil in seawater on salmonid predatory behavior. Coho salmon (Oncorhynchus kisutch) were chosen as predators. This species has been identified as a primary predator of juvenile salmonids in seawater. The studies indicated that exposure to the seawater-soluble fraction (SWSF) of Cook Inlet crude oil can significantly impair the capturing of prey by Coho salmon predators. An interesting observation associated with that behavioral difference was that levels of the parent hydrocarbons were markedly higher in the tissues of the oil-exposed eater subgroup than in those of the noneater oil-exposed subgroup. Brain and liver hydrocarbon concentration differences between eater and noneater subgroups suggest differential uptake, excretion and/or metabolism of these chemicals. If the lower hydrocarbon levels in the noneaters reflect metabolism and, therefore, the activity of the mixed function oxidase enzymes, differential induction could be a possible explanation. Since the eater subgroup had much higher tissue concentrations of the parent hydrocarbons in both brain and liver than themore » noneaters, it appears unlikely that the parent hydrocarbons were the xenobiotics primarily influencing feeding behavior. The lower concentrations of the parent hydrocarbons in the noneater subgroup suggest that the metabolic products of the crude oil may have been responsible for the cessation of feeding. These preliminary results are in apparent contrast with previously reported findings that acute neurotoxic effects and behavioral changes were related to accumulation of the parent compounds rather than nonconjugated metabolites of the parent compound.« less