Porcelain crabs may reduce oyster recruitman

NSF Fellow: Savannah Rhoades, University of South Florida

Mentor: Dr. John Carroll

Petrolisthes armatus, more commonly referred to as the porcelain crab, is an invasive species that can be found across oyster reefs from Florida into southern North Carolina. Their expanding range is thermally controlled, and as climate change continues, they will likely continue northward expansion. Porcelain crabs can have very high densities, up to 11,000 per square meter in some areas. Importantly, these crabs are suspension feeders, which puts them into potential competition with oysters, and may even filter out eggs and larvae. In this study, we examined whether porcelain crabs affect oyster recruitment by exploring food preference in the lab and the impacts of crab abundance on new oyster recruitment in the field. While we initially established 3 different crab treatment levels, our cage design ultimately proved ineffective at excluding crabs. Thus, we explored oyster recruitment against cream abundance and biomass As crab biomass increased, the number and size of oysters decreased. While our data only explained 19 and 15% of the variability and were not statically significant, these trends may be biologically meaningful. Our attempts to determine food preference was challenging, while it seemed as though the crabs could consume oyster eggs in some experimental units, results were highly inconsistent. This was likely due to limitations on our experimental design and challenges associated with working with small organisms. Overall, more studies can be done to see if porcelain crabs affect oyster recruitment and we hope that our project will help others in determining proper methodology.