Delayed effects on growth and marine survival of pink salmon Oncorhynchus gorbuscha after exposure to crude oil during embryonic development

We report delayed effects on the growth and marine survival of pink salmon Oncorhynchus gorbuscha, which were exposed to oil as embryos under conditio ns similar to those observed after the 'Exxon Valdez' oil spill. Pink salmo n eggs were incubated in water that became contaminated with polynuclear ar omatic hydrocarbons (PAHs) after percolating through gravel coated with wea thered oil. Weathering ensured that the PAH composition of the water was do minated by alkyl-substituted naphthalenes and larger compounds. Most surviv ors of the exposures appeared healthy, and were released to the marine envi ronment with coded-wire tags. Their survival was evaluated when they return ed at maturity 2 yr later. Other survivors, also healthy in appearance, wer e retained in net pens to measure delayed effects on growth during the earl y juvenile stage. Pink salmon exposed to an initial concentration of total PAH equal to 5.4 ppb experienced a 15 % decrease in marine survival compare d to unexposed salmon. A delayed effect on growth was measured in juvenile salmon that survived embryonic exposure to doses as low as 18 ppb PAH. Redu ctions in juvenile growth could account for the reduced marine survival obs erved in the released fish. The demonstration of delayed effects on growth and survival support claims of delayed effects in pink salmon after the 'Ex xon Valdez' oil spill, and indicate the potential for population-level effe cts resulting from embryonic exposure to oil.