Olympia Oyster Restoration: Habitat Suitability and Climate Considerations

Thesis (Master's)--University of Washington, 2020Oyster habitat suitability index (HSI) models can support conservation and restoration planning, siting aquaculture projects, and other purposes. In recent decades, partners have undertaken efforts to restore populations of Olympia oysters (Ostrea lurida) in the Salish Sea. Olympia oyster restoration projects are more likely to become self-sustaining and contribute to overall population growth when sited in locations with optimal conditions. This study describes the development and application of a preliminary HSI model for Olympia oyster restoration in the southern Salish Sea. Environmental data and tolerance thresholds for six habitat variables – tidal elevation, salinity, temperature, current velocities, low salinity events, and water residence time – are compiled to create a geospatial index of suitability. This study identifies potentially suitable habitat throughout the study region. HSI output is compared to oyster observations and abundance at restored sites to evaluate accuracy and consider potential applications. While predictions of suitable habitat and oyster presence and abundance align in some locations, there are limitations to using the index as a tool for restoration planning. In addition, this study provides an example of how the HSI may be used to explore climate change considerations for restoration projects. The results of this study, in combination with other methods and information, may provide a useful preliminary tool for identifying potentially suitable locations for Olympia oyster restoration projects in the region