Stable nitrogen isotope (δ15N) data from sediment cores taken in clear-water Upper Russian Lake (Kenai River Watershed, Alaska, USA) indicate that sockeye salmon (Oncorhynchus nerka) populations varied significantly over the past 4000 years, with a prominent ~ 650-year period of lower salmon abundance from ~ 100 BCE to 550 CE. Sediment characteristics during this ~ 650-year interval reflect glacial sediment input, which may have contributed to the salmon decline by degrading spawning habitat and reducing carrying capacity. The decline, however, coincides with large reductions in sockeye salmon abundance identified previously in Karluk and Akalura lakes on Kodiak Island, > 400 km southwest, supporting the possibility of regionally synchronous, multi-centennial production regimes that may originate from shifts in oceanographic conditions such as biological productivity in the northeastern Pacific Ocean. Under such a scenario, coincidence with watershed glacial activity indicates a common driver, i.e. regional climate change. Climate conditions that led to significant glacial advances in this part of the Kenai Peninsula (cold and/or wet conditions) may have also created unfavorable ocean conditions during critical periods in the marine phase for these stocks of Gulf of Alaska sockeye salmon. Future climate projections and management strategies should focus on how climate regimes impact not only prey availability for salmon at sea, but also local conditions for spawners and juveniles.
Bibliographical noteFunding Information:
Acknowledgements This analysis was part of a larger project funded by Alaska EPSCoR National Science Foundation award #O1A-1208927 and the State of Alaska. Support for Bruce Finney was assisted by NSF award #1521365. We thank Kristi Wallace from USGS for tephra analysis, as well as use of her tephra lab for a variety of sampling activities. We acknowledge the many researchers who work for the Alaska Department of Fish and Game and collected long-term data on commercial and sport catch and escapement of Kenai River and Russian River salmon, and especially Mark Willette for providing initial guidance. We also thank Dr. David Fortin, Nore Preat, Koen Du Ryker, Phillip Kempf, Nicole Warner, Courtney Breest, Scott Cunfer, Nancy McCarthy, and Frank McCarthy for field and laboratory assistance. The findings and conclusionsin this article are those of theauthors and do not necessarilyrepresent the view of the U.S.Fish and Wildlife Service.
© 2018, The Author(s).
Copyright 2018 Elsevier B.V., All rights reserved.
Continental Scientific Drilling Facility tags