Published: Jan 1995
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Pacific herring, Clupea pallasi, spawn along hundreds of kilometres of shoreline in Prince William Sound. Herring eggs incubate in intertidal and shallow subtidal areas attached to kelp and eelgrass. In April 1989, following the Exxon Valdez oil spill, there was potential in Prince William Sound for localized effects on spawning herring, their eggs, and the hatching larvae. Field and laboratory investigations in 1989 and 1990 were designed to assess potential injury to Prince William Sound herring by testing for differences between oiled regions and unoiled reference areas and by relating biological response variables to the concentrations of polycyclic aromatic hydrocarbons (PAH) in eggs-on-kelp samples. Hydrocarbon analyses and laboratory incubation were conducted on eggs-on-kelp samples from Prince William Sound and Sitka Sound. The eggs and hatching larvae were examined to evaluate several response variables: egg development, hatch, larval survival, abnormal development of larvae, larval length, and larval yolk-sac volume.
Analysis of 1989 shoreline surveys indicate that about 96% of the total spawn length (158 km) in Prince William Sound occurred along shorelines with no oiling, and less than 1% of the 1989 total spawn length occurred along shorelines with moderate to heavy oiling. Analysis of shoreline oiling in both 1989 and 1990 from all surveys indicates that about 90 to 91% of the total 1989 spawn length occurred along unoiled shorelines. Effects on herring eggs were minor in 1989 even in oiled areas. No significant relationship was found between 1989 PAH burdens in eggs-on-kelp samples and 9 out of 10 biological response variables. In 1989, significantly lower proportions of developed eggs were observed for Cabin Bay samples visibly contaminated with tarry deposits. The location where these effects were seen represented less than 2% of total 1989 spawn length. No effects of the spill on herring were evident in 1990. No significant relationship was found between 1990 PAH burdens and the seven biological response variables studied. Biological response variables from Sitka Sound were either not significantly different from or significantly lower (more adverse) than those from Prince William Sound.
Our 1989 and 1990 results are consistent with the low exposure of herring to oil and do not indicate an extent of injury that would be significant to the Prince William Sound herring population. The biomass and harvests of Prince William Sound herring had reached record high levels in the three years immediately following the spill so that the minor effects observed in 1989 did not translate into decreases in the population level.
Pacific herring, Clupea pallasi, oil spill, Exxon Valdez, Prince William Sound, fish eggs, fish larvae
Senior Research Scientist, Battelle/Marine Sciences Laboratory, Sequim, Washington
Senior Research Scientist, Institute of Marine Research, Flodevigen Marine Research Station, His,
Associate Professor, Center for Quantitative Sciences, School of Fisheries, University of Washington, Seattle, Washington