Marine Ecology Progress Series
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DOI: https://doi.org/10.3354/meps14972
copiedArchaeological evidence across four millennia indicates recent erosion of Chinook salmon age structure in California
- Malte Willmes
- Flora Cordoleani
- Anna M. Sturrock
- Emily K. Chen
- William H. Satterthwaite
- Rachel C. Johnson
- Jelmer W. Eerkens
- George Whitman
- Carson Jeffres
- Eric P. Palkovacs
- Joe Jessie Ruiz Jr.
- James A. Hobbs
- Levi S. Lewis
- Jeff Rosenthal
ABSTRACT:
Chinook salmon Oncorhynchus tshawytscha provide crucial ecosystem services, but their populations are in steep decline throughout their native range. Recent decades have seen widespread erosion of age structures, but the lack of long-term baselines makes it difficult to assess this change. We collaborated with the Estom Yumeka Maidu Tribe of Enterprise Rancheria and used otoliths to reconstruct changes in age structure for California Central Valley Chinook salmon over the last 4 millennia. Specifically, we compared the returner age structure of present-day hatchery and natural populations in the Feather and Yuba rivers (2002-2020) with archaeological data from the same watershed, spanning the Middle-Holocene (1800-1000 BCE), Late-Holocene (500-1770 CE), and post-European-contact (1770-1870 CE) periods. We observed a shift to younger ages, from dominantly age-4 returners in the archaeological samples to age-3 fish in both hatchery and natural populations today. The recent time period also shows reduced variance and diversity in return ages compared to the post-European-contact time period, which has the most robust sample size of the archaeological collection. The shift toward younger ages in returning fish may have caused losses in productivity, while the decrease in variance and diversity may have reduced their resilience to environmental stochasticity. The erosion of age structure since European contact suggests anthropogenic factors—such as loss of freshwater and estuarine habitats, and industrialized ocean fishing and hatcheries—as potential contributors. Incorporating archaeological data into ecological assessments can help guard against hidden shifting baselines and inform restoration targets for more resilient populations.
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Malte Willmes (Corresponding Author)
- Institute of Marine Sciences, University of California Santa Cruz, 115 McAllister Way, Santa Cruz, CA 95064, USA
- Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway
Flora Cordoleani (Co-author)
- Institute of Marine Sciences, University of California Santa Cruz, 115 McAllister Way, Santa Cruz, CA 95064, USA
- National Marine Fisheries Service, Southwest Fisheries Science Center, 110 McAllister Way, Santa Cruz, CA 95064, USA
Anna Sturrock (Co-author)
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
Emily Chen (Co-author)
- Department of Environmental Science, Policy, & Management, University of California Berkeley, 130 Mulford Hall #3114, Berkeley, CA 94720, USA
William Satterthwaite (Co-author)
- National Marine Fisheries Service, Southwest Fisheries Science Center, 110 McAllister Way, Santa Cruz, CA 95064, USA
Rachel Johnson (Co-author)
- National Marine Fisheries Service, Southwest Fisheries Science Center, 110 McAllister Way, Santa Cruz, CA 95064, USA
- Center for Watershed Sciences, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
Jelmer Eerkens (Co-author)
- Department of Anthropology, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
George Whitman (Co-author)
- Center for Watershed Sciences, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
Carson Jeffres (Co-author)
- Center for Watershed Sciences, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
Eric Palkovacs (Co-author)
- Institute of Marine Sciences, University of California Santa Cruz, 115 McAllister Way, Santa Cruz, CA 95064, USA
Joe Ruiz Jr (Co-author)
- Estom Yumeka Maidu Tribe of Enterprise Rancheria, CA 95966, USA
James Hobbs (Co-author)
- Department of Wildlife, Fish, and Conservation Biology, University of California Davis, 1 Shields Ave., Davis, CA 95616, USA
Levi Lewis (Co-author)
- Department of Wildlife, Fish, and Conservation Biology, University of California Davis, 1 Shields Ave., Davis, CA 95616, USA
Jeff Rosenthal (Co-author)
- Far Western Anthropological Research Group, 2727 Del Rio Place, Suite A Davis, CA 95618, USA
Handling Editor:
Jana Davis, Annapolis, Maryland, USA
Reviewers:
3 anonymous referees
Acknowledgements:
We express our thanks to the Estom Yumeka Maidu Tribe of Enterprise Rancheria for their collaboration on this project. Furthermore, we thank Michael Bessette, Executive Director of the Sutter Butte Flood Control Agency, for his support. We thank Kimberly Evans and Larisa Thacher for assisting in the ageing of the otolith samples. We also thank Dr. Stuart Munsch, who provided insightful comments and constructive feedback on an earlier version of the manuscript. Financial support was provided by the Delta Stewardship Council (DSC-21022). A.M.S. was supported by a UK Research and Innovation grant (MR/V023578/1).