Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8647
Title: Evaluating signals of oil spill impacts, climate, and species interactions in Pacific herring and Pacific salmon populations in Prince William Sound and Copper River, Alaska
Author: E. J. Ward, Milo Adkison, Jessica Couture, Sherri C. Dressel, Mike Litzow, Steve Moffitt, Tammy Hoem Neher, John Trochta, Rich Brenner
Publication Year: 2017
Journal: PLoS ONE
Keywords: exxon valdez,oil spill,herring,salmon,productivity,Spawner-recruit relationship
Abstract:

The Exxon Valdez oil spill (EVOS) occurred in March 1989 in Prince William Sound, Alaska, and was one of the worst environmental disasters on record in the United States. Despite long-term data collection over the nearly three decades since the spill, tremendous uncertainty remains as to how significantly the spill affected economically-significant fishery resources.  Pacific herring and wild Pacific salmon populations in Prince William Sound declined in the early 1990s, and have not returned to the population sizes observed in the 1980s. Attributing these changes entirely to the oil spill has been difficult because a number of other physical and ecological drivers are confounded temporally with the spill; some of these drivers include changing climate or alternating climate regimes, increased production of hatchery salmon in the region, and increases in predator populations. Using data pre- and post-spill, we applied time-series methods to evaluate support for whether and how herring and salmon recruitment has been affected by each of five drivers (1) effects of density dependence, or decreasing population growth rate at increasing population density (2) immediate and / or prolonged impacts of the EVOS event, (3) effects of interspecific competition on juvenile fish, (4) effects of predation from adult fish or other predators, and (5) impacts of changing environmental conditions. Our results showed support for intraspecific density-dependent effects in herring, sockeye, and Chinook salmon. The inclusion of an oil spill effect was supported for pink but not supported for other salmon or herring populations. The strongest predictor of herring recruitment was freshwater discharge into Prince William Sound, supporting the idea that herring in the region experienced a series of nutritionally related recruitment failures – both before, during, and after EVOS.the Exxon Valdez spill. Examining historical data, there is some evidence for Prince William Sound experiencing similar dynamics over the last century (a warm regime, resulting in high freshwater discharge, poor herring recruitment, followed by a fishery collapse). These results highlight the need to better understanding the interactions between nearshore species and freshwater inputs, particularly as they relate to climate change and increasing water temperatures. 

Theme: Recovery and rebuilding of marine and coastal species
Foci: Describe the relationships between human activities and species recovery, rebuilding and sustainability.
Develop methods to use physiological, biological and behavioral information to predict population-level processes.