Potential population-level impacts of future oil spills on Pacific herring stocks in Puget Sound

Abstract

Oil spills threaten the productivity of marine forage fish that spawn in shallow shoreline habitats. In western North America, this includes Pacific herring (Clupea pallasii), a keystone species for marine food webs. Crude oil-derived polycyclic aromatic hydrocarbons (PAHs) are highly toxic to herring embryos and larvae. Despite our understanding of individual-based toxicity, the impacts of oil spills at the population-scale remain uncertain. We modeled the response of Puget Sound herring stocks to simulated oil spills and found that declining stocks are less likely to withstand the short-term impacts of a small, localized spill. Moreover, conventional stock assessment methods may only detect large population declines in response to high rates of mortality in a single year, or sustained losses across multiple year classes. We discuss the importance of herring life history and environmental variation on the predictive usefulness of conventional population modeling as a basis for estimating injury to highly variable marine forage fish resources.