Project ID: WA2014_38
Lead Investigator: Jeffrey Falke, USGS; Peter Westley, University of Alaska Fairbanks (UAF)
Collaborators: Morgan Sparks & Milo Adkinson, UAF; Krista Bartz & Dan Young, National Park Service; Thomas Quinn, Daniel Schindler, & Michael Tillotson, University of Washington; Thomas Reed, University College Cork
Project Duration: 2014-2016
Viable sockeye salmon populations are critical to the economy, culture, and freshwater ecosystems of Bristol Bay in Western Alaska, and it is unclear how populations might respond to warming temperatures during the critical life history stages of spawning and embryo incubation. The overarching goal of the project was to understand how both recently experienced and projected water temperatures might influence population-specific patterns of embryo incubation, timing of hatching and fry emergence, and sockeye salmon embryo survival. Additionally, the project explored the potential for adaptation in smolting size threshold, a heritable life history trait influencing whether an individual migrates to the ocean after either one or two years of freshwater rearing.
The project 1) synthesized information on spawn timing of discrete populations and water temperatures to predict timing of juvenile hatching and fry emergence under a range of conditions observed in the Kvichak and Wood River watersheds; 2) predicted changes in water temperatures likely to be experienced by salmon populations in Iliamna Lake using downscaled Global Circulation Models under plausible scenarios of CO2 emissions through the year 2099; 3) conducted a controlled laboratory experiment to quantify the population-specific functional responses between timing of hatching and embryo survival under scenarios of freshwater warming; and 4) assessed probabilities of persistence and likelihood for life history adaptation (smolting size threshold) to warming temperatures using individual-based eco-evolutionary models parameterized based on representative sockeye salmon populations in the Kvichak watershed.
Key insights include: i) a new understanding of the range of diversity in hatching and emergence that occurs across the landscape of Bristol Bay (e.g. fish are estimated to hatch between October and May depending on site-specific temperature and timing of adult spawning); ii) evidence suggesting that spawning timing is more closely correlated to average summer water temperatures and not the temperatures embryos experience during incubation; iii) estimates that hatching timing for one population is predicted to advance approximately one week by 2099 under plausible warming scenarios; iv) embryo survival is not likely to be affected by water temperatures regimes predicted into the future, v) that populations exhibit remarkable plasticity in developmental rates in response to water temperatures and to a lesser extent exhibit family-specific (heritable) developmental rates that lead to responses consistent with gene x environment interactions, and vi) that the size threshold for smolting may shift to a larger size in the face of warming water temperatures given trade-offs between freshwater growth and size-dependent marine mortality; however, the pace of evolution depends on the strength of size-selective mortality at sea and heritability of the size-dependent smolting threshold trait. This project contributes to the mounting evidence that habitat diversity, and the heritable and plastic phenotypic diversity that ensues, is vital to the long-term persistence of salmon dominated ecosystems of Western Alaska.
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