Are Bristol Bay sockeye salmon responses to climate change predictable?

Background/Question/Methods: Research has shown that climate change has already caused detectable changes to ecosystems throughout Alaska. As warming continues, it is likely to lead to changes in marine and freshwater aquatic ecosystems and potentially impact sockeye salmon populations in Bristol Bay, Alaska. Sockeye salmon are vulnerable to climate change throughout their life cycle in both freshwater and marine habitats.  Fundamental changes in both habitats could engage a suite of cascading effects that could influence conditions for salmon spawning, rearing, and survival.  Effects of climate change in the marine and freshwater environments for salmon are likely to interact in complex ways.  Research across the geographic range of sockeye salmon is identifying potential climate effects on this species, but responses are often complex, and may be region and scale dependent.  In order to better predict how sockeye salmon will respond to climate change, we synthesized the peer-reviewed literature on the potential effects of climate change on sockeye salmon with a conceptual model that encompasses the full life cycle of salmon across the marine and freshwater environments. We sought to identify key pathways from the conceptual model where agreement on predicted effects is converging, and pathways where projected impacts are equivocal, regionally-specific, or poorly understood.

Results/Conclusions:

Projected freshwater changes include altered water temperatures and hydrologic regimes, which are linked to changes in migration, prey availability, and salmon development. Within the literature, sockeye salmon responses are not uniform, and the direction of response can vary with season and geo-climatic setting. Throughout the region, the responses are likely to be population specific due to population variability; the variability may be essential for salmon resilience in the face of future change. Additionally, in the marine environment, climate patterns influence sea surface temperature and impact salmon, likely due to the timing and abundance of prey availability. The effect of ocean acidification on salmon populations remains unknown, but may include shifts in prey species. Few studies have evaluated the interaction between freshwater and marine environments, which is necessary in understanding the overall salmon response to climate change. Our results highlight areas of emerging consensus and key remaining uncertainties of climate change impacts on sockeye salmon in Bristol Bay, a region supporting a globally-valuable fishery facing increasing human demands for natural resources. Disclaimer: The views expressed in this abstract are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.