Exxon Valdez Oil Spill Restoration Project annual report

Auke Bay Laboratory (Juneau, Alaska)

This project examines the effects of oil exposure during embryonic development on the straying, survival to spawning, and gamete viability of pink salmon (Oncorhynchus gorbuscha). The objectives for the straying component are to conduct a related series of controlled experiments on straying of pink salmon to detennine the role of oil and other factors (stock, transplant, and tagging) on straying; and to use the results to interpret the high straying rates observed for wild populations of pink salmon in Prince William Sound (PWS) after the Exxon Valdez oil spill. In FY95, the objectives ofthe project were to (1) set up the incubation and oil exposure array, and expose pink salmon embryos from the 1995-brood to oiled gravel; and (2) test fry capture and adult sampling and enumeration techniques. Treatment levels of oil were based on the results of Restoration Project 191B; relatively low dosages were used to ensure high survival to fry emergence. Small but significant reductions in survival of pink salmon embryos were detected, however, even at nominal dosages as low as 0.4 g oil per kg of gravel. Fry capture and adult sampling and enumeration techniques were successfully tested. Based on the return and recovery rate in streams in the Little Port Walter vicinity of pink salmon of fish tagged for Restoration Project 95076, a model was constructed to examine the ability of the experimental design to detect differences in straying rates among treatments. Results from Restoration Project 191 B demonstrate a long-term effect ofoil on growth, and suggest that incubating in oiled gravel reduces marine survival and reproductive ability.

Professional Paper

National Marine Fisheries Service (NMFS)