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Exxon Valdez Oil Spill Fish Projects:
Pink Salmon Toxicity to Life History

  picture of a healty pink salmon fry picture of a PAH mutated pink salmon fry

Principal Investigators:

Mark Carls
(907) 789-6019

Ron Heintz

View FY00 Proposal

View Poster:  Pink Salmon Eggs & PAH

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For 4 years after the Exxon Valdez oil spill, Alaska Department of Fish and Game (ADF&G) biologists recorded elevated mortalities among pink salmon embryos incubating in contaminated sections of affected streams. The persistence of these observations was contrary to expectations because streambed contamination was thought to be minimal, and salmon eggs were not considered sensitive to polynuclear aromatic hydrocarbons (PAH).

In 1992, we began examining the plausibility of the ADF&G observations by incubating pink salmon eggs in gravel contaminated with known quantities of oil. After following three brood years, we concluded that pink salmon eggs are sensitive to low concentrations of the PAH that characterize weathered oil and that effects can be observed in eggs incubating downstream from the oil source.

Embryos exposed to aqueous PAH concentrations of 1.0 ppb demonstrated a twofold increase in mortality compared with unexposed embryos and a 10% reduction in growth during their first 6 months in salt water. Fish initially exposed as embryos to aqueous PAH concentrations of 19 ppb from the 1993 and 1995 broods experienced marine survivals 15% to 60% lower, respectively, than unexposed fish. Estimates reveal that exposed cohorts produced 38% and 42% fewer mature adults than unexposed cohorts in the 1993 and 1995 broods, respectively. Observations of reduced growth suggest further reductions in reproductive potential through reduced fecundity.

Our laboratory observations indicate the plausibility of the ADF&G observations. These conclusions are further supported by knowing that the minimum effective concentrations of PAH identified in our studies are bracketed by the range of contamination levels reported in and around pink salmon streams in PWS for at least 4 years after the spill.

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