Egg-larval mortality of Pacific herring in Prince William Sound, Alaska, after the Exxon Valdez oil spill

We tested the hypothesis that instantaneous daily rates of egg-larval mortality of Pacific herring, Clupea pallasi, were greater at two oil-exposed sites than at two nonexposed sites. Egg-larval mortality is defined as the ratio of larval density at hatch to mean egg density divided by the number of elapsed days between the dates of the two estimates. There were significant differences between sites in egg density, small differences between sites in mean larval length, and no oil-related differences between sites in the rates of larval growth and loss. However, mean egg-larval mortality in the two oiled areas was twice as great as in the two nonoiled areas, and larval growth rates were about half those measured in populations from other areas of the north Pacific Ocean. These findings support the hypothesis of oil injury to herring embryos and larvae.