When Endangered Species Collide: Ecosystem Restoration in Prince William Sound, Alaska

A population crash of Pacific herring in Prince William Sound (PWS) was detected in 1993, four years after the tanker, Exxon Valdez, spilled 42 million liters of crude oil into PWS. Only recently has there been strong evidence that the herring decline begin immediately after the oil spill. On the basis of this new evidence, the Exxon Valdez Oil Spill Trustee Council (EVOS TC), which oversees restoration efforts, has recognized that the condition of the herring stock is critical. Research at the Prince William Sound Science Center over past seven years has shown strong linkages between herring abundance and the numbers of Steller sea lions foraging in PWS. The evidence further suggests that the PWS herring collapse had a detectable impact on the endangered western stock of Steller sea lions. More recent evidence suggests that humpback whale predation on herring in PWS has contributed annual mortality to the herring population that is comparable to historic commercial fishery removals and may be a major factor in the lack of recovery. Clearly central to the challenge of herring and associated ecosystem restoration is dealing with impacts of marine mammals, who are themselves endangered.