Despite long term data collection in the Gulf of Alaska since the Exxon Valdez Oil Spill in 1989, the degree to which the spill affected fish populations remains controversial. Productivity of herring and some species of salmon have declined compared to the late 1970s or 1980s, but it is unclear if this reduction is a result of the oil spill. In a recent PLOS ONE publication, the NCEAS Gulf of Alaska Portfolio Effects Working Group examined herring and salmon productivity over time to determine if lack of recovery for these species was due to the oil spill or other environmental factors such as freshwater discharge or competition.
The researchers found no support for long term population level impacts of the oil spill on salmon and herring productivity. Instead, they discovered herring productivity was most strongly affected by increased freshwater discharge into the Gulf of Alaska, where peaks in discharge corresponded with recruitment failures. Additionally, the increase of hatchery pink salmon had a negative effect on wild sockeye salmon productivity due to competition for resources. Thus, while these populations have been affected by other environmental parameters, there is lack of evidence that the oil spill has had negative impacts at the population level.
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
Ward, E.J., Adkison, M., Couture, J., Dressel, S.C., Litzow, M.A., Moffitt, S., Neher, T.H., Trochta, J., Brenner, R.
PLOS ONE, March 2017, doi: 10.1371/journal.pone.0172898
Photo Credit: Rich Brenner