Oyster drill (Stramonita haemastoma complex) habitat preferences in a shallow coastal estuary

Southern oyster drill snails (Stramonita haemastoma complex) are nuisance organisms within the Gulf of Mexico. This is due to their damaging impact on recovering and farmed oyster (Crassostrea virginica) populations, which are one of the drills’ main food sources. Oyster reef recovery and increased aquaculture production are priorities for Mississippi and the wider northern Gulf coast. The Grand Bay National Estuarine Research Reserve (NERR) hosts multiple oyster reef restoration sites within its boundaries, yet no comprehensive survey of oyster drill abundance has been conducted in this area to date. Additionally, knowledge of oyster drill preferences for sediment composition within their wider habitat is limited. The aim of this project was to determine sediment and water quality preferences of oyster drills in the NERR, as well as identify hotspots. Over 6 weeks, we conducted a field survey of the oyster drill population with 36 traps grouped along 12 transects, spread across 3 areas of the estuary - Bangs Lake (BL), Bangs Bayou (BB) and Point aux Chenes Bay (PAC), with reef restoration sites occurring in BB and PAC. In conjunction with traps, we measured relative depth, transect-event water quality, and collected sediment from each trap site. Drills were more abundant in mid - south PAC and east BL. Across other transects, they were more often found in mid-transect locations, which were also often the mid-depth of each transect. Our findings on drill abundance, sediment characteristics, water quality and site preferences can be used to inform future reef restoration efforts and drill mitigation techniques.