To conserve coastal foundation species, it is essential to understand patterns of distribution and abundance and how they change over time. We synthesized oyster distribution data across the west coast of North America to improve conservation strategies for the native Olympia oyster (Ostrea lurida), and also gathered information on feral populations of the non-native Pacific oyster (Magallana gigas ), the only widespread non-native oyster and a notorious global invader, occurring within this range.
We designed a user-friendly portal for data entry into ArcGIS Online and collected oyster records from unpublished data submitted by oyster experts and entered by interns from the published literature, while self-quarantining during the early phase of the COVID-19 pandemic. The resulting database contained over 2,000 records, which we used to examine spatial and temporal patterns and have made publicly available via an interactive web-based map.
Comparing records from pre-2000 vs. post-2000, we found that O. lurida significantly decreased in abundance and distribution, while M. gigas increased significantly. Currently the distribution and abundance of the two species are fairly similar, despite one species being endemic to this region since the Pleistocene, and the other a new introduction. We mapped the networks of sites occupied by oysters b ased on estimates of larval dispersal distance, and found that these networks were larger in Canada, Washington, and southern California than in other regions. We recommend restoration to enhance O. lurida network size where it is small, and increase abund ance where it declined. We also recommend approaches that restore natural biogenic beds to mudflats and sandflats especially in the southern range, where native oysters are currently found most often on rip rap and other anthropogenic structures.