Influence of Salinity on Eastern Oyster Recruitment in the Lewes-Rehoboth Canal

• Sarah Hemminger, Marine Science, University of Delaware

• Edward Hale, School of Marine Science and Policy, University of Delaware, University of Delaware

Eastern oysters (Crassostrea virginica) are ecosystem engineers that play a critical role in estuarine ecosystems by creating reef habitat, improving water quality through filtration, contributing to nutrient cycling, and stabilizing shorelines. Successful recruitment of oyster larvae is essential for sustaining natural populations and supporting restoration efforts, yet recruitment often varies across estuarine systems due to differences in environmental conditions and hydrodynamic connectivity. This study investigates spatial and seasonal patterns of Eastern oyster recruitment within the Lewes-Rehoboth Canal system and evaluates relationships between recruitment and environmental conditions, with particular emphasis on salinity. Standardized shell collectors consisting of mesh bags containing clean oyster shells were deployed within crab pots at five monitoring locations representing varying degrees of connectivity to Delaware Bay. Shells were collected weekly and examined under a flex-arm magnifier for the presence of newly settled oyster larvae (spat). Water quality measurements were collected using a YSI multiparameter instrument during deployment and retrieval, while continuous measurements of temperature and conductivity were recorded using HOBO data loggers throughout the study period. Preliminary observations indicate minimal oyster recruitment during the first five weeks of sampling, with the first evidence of settlement occurring during Week 6 when oyster spat were detected on a single shell at the Boat Basin site. Initial deployment measurements showed relatively uniform salinity among sampling locations (29.6–30.3 ppt), while dissolved oxygen varied substantially among sites. Recruitment monitoring and environmental data collection are ongoing. Future analyses will integrate continuous environmental data to evaluate how variation in salinity, temperature, dissolved oxygen, and pH influences oyster recruitment throughout the canal system. Findings from this study will improve understanding of the environmental factors influencing oyster recruitment within Delaware’s interconnected coastal waterways and may help inform future oyster restoration and management efforts.