Review of Studies on Oil Damage To Prince William Sound Pink Salmon

ABSTRACT In the tenth year following the Exxon Valdez oil spill, differences of opinion still exist about injuries to pink salmon. It was alleged that exposure to oil reduced growth of fry and induced mortality in eggs. The authors reexamined the allegation that injury occurred and have concluded that insufficient consideration was given to other factors that affected results in the studies from which these allegations were drawn. The inability to track temperature differences and the unknown ages of fry precluded assessment of oil effects on growth during early marine residence. Reported higher egg mortality and long-term injury alleged to have resulted from oil exposure during incubation were confounded by the mortality of eggs that occurred as an artifact of the sampling procedure, unrelated to oil effects. The authors concluded that injury to incubating pink salmon embryos and reduced fry growth were based on an incomplete assessment of other factors that influenced these results. This evidence is supported by other research that has disclosed no oil effects on incubating eggs. Among these were studies that showed measured oil concentrations reaching the incubation substrate were 14 to 7,600 times below the lethal threshold. The seven largest runs in the history of Prince William Sound (PWS), Alaska have returned in the 10 years following the spill, which ultimately demonstrated the lack of measurable effect of the oil spill on pink salmon. The authors suggest that the allegation of oil-induced injury to PWS pink salmon needs to be reconsidered in light of these analyses.