Archaeological evidence across four millennia indicates recent erosion of Chinook salmon age structure in California

Chinook salmon (Oncorhynchus tshawytscha) provide crucial ecosystem services, but their populations are in steep decline throughout most of their native range. These anadromous fish express a complex age structure, increasing resilience to disturbances. Recent decades have seen widespread diversity loss, but the lack of long-term baselines makes it difficult to assess this change. In this study, we collaborate with the Estom Yumeka Maidu Tribe of Enterprise Rancheria and use fish otoliths (ear stones) to reconstruct changes in age structure for California Central Valley Chinook salmon covering the last 4 millennia. Specifically, we compare the returner age structure of present-day hatchery and natural populations in the Feather and Yuba River (2002-2020) with archaeological data from the same watershed, spanning the Middle-Holocene (1800-1000 BCE) to the Late-Holocene (500-1770 CE) and Post-European-Contact (1770-1870 CE) time periods. We observe a shift to younger ages, from dominantly..., , # Archaeological evidence across four millennia indicates recent erosion of Chinook salmon age structure in California

Dataset DOI: [10.5061/dryad.rxwdbrvng](10.5061/dryad.rxwdbrvng)

## Description of the data and file structure

This dataset contains the data and scripts for the analyses performed in “Archeological evidence across four millennia indicates recent erosion of Chinook salmon age structure in California.”

### Files and variables

Files are in a single file 'meps14972.zip' and need to be extracted. There is an R project file included and several subfolders that are referenced in the script. The `data folder` contains the data used for the analyses, the `scripts folder` contains the R scripts, and the `outputs folder` contains all figures and tables generated from this R project. Files in the `outputs folder` will get overwritten with subsequent runs of the scripts and should thus not be edited manually.

**Scripts**

**01_data_analysis**: Data preparation, homogenization...,