A century of climate change and freshwater growth in juvenile sockeye salmon from Bristol Bay, Alaska

  Lack of long data records currently impedes our understanding of how aquatic populations and ecosystems respond to ongoing climate change. An additional challenge is to understand how geographic context controls ecological responses to changing environmental drivers. Sockeye salmon in Bristol Bay, Alaska have become increasingly abundant over the last century as nursery lakes have warmed and become more productive. However, population responses are widely variable among the watersheds across the region. For example, the Nushagak River jumped from producing 5% of the Bristol Bay sockeye to nearly 20% in 2022, while sockeye populations in the nearby Wood River began increasing gradually in the 1980s. We hypothesize that the differences between these two river systems is a function of local watershed control on climate forcing and local ecological responses to warming lakes. The large, cold lakes that feed the Nushagak and Wood Rivers are oriented in a N-S pattern, with the Nushagak lakes located north of the Wood River lakes, and nearly 100km farther from the ocean. We analyzed a century-long (1917-2023) archive of sockeye salmon scales to reconstruct juvenile growth in fresh water to assess the lake-specific responses to warming climate. Preliminary results support the hypothesis that the sequential population response is attributed to landscape-filtered climate shifts that have positively affected salmon growth: that the natal lakes closer to the coast (Wood lakes) experienced a climate shift sooner than the inland lakes (Nushagak lakes).

Presentation Preference: Oral

Primary Presenter: Emma Christman, University of Washington (echristm@uw.edu)

Authors:

Emma Christman, University of Washington  (echristm@uw.edu)

Daniel Schindler, University of Washington  (deschind@uw.edu)