Conditions that promote oyster settlement coincide with areas of high boating activity in a developed coastal habitat

Global decline of oyster reefs prompted interest in restoring these valuable habitats, which stabilize shorelines and are home to diverse fauna. Recent efforts highlight the need for careful selection of effective restoration sites that will promote oyster growth and maximize shoreline stabilization. Boating is a significant contributor to oyster mortality in Mosquito Lagoon, Florida, USA, where energy from boat wakes dislodge oysters shoreward and create dead margins of disarticulated oyster shell. These boat wake effects are well-documented; however, few studies concentrated on oyster recruitment in Northern Mosquito Lagoon, which is bordered by developed coastline along a heavily trafficked boating channel. In this 20-week field study, we compared the settlement density of eastern oysters, Crassostrea virginica, on concrete substrate at four sites in Northern Mosquito Lagoon that varied in boating intensity (low and high) and proximity to existing C. virginica reef (≤ 1 m and ≥ 49 m). Surprisingly, oyster settlement was greater at sites with high boating intensity. However, elevated recruitment may have been due to increased tidal flow and potential larval supply in the boating channel, rather than a direct effect of boat wakes. Proximity to existing C. virginica reef also had a positive effect on oyster settlement and a negative effect on barnacle settlement. Our results suggest that ideal sites for recruitment and juvenile survival of oysters coincide with areas of high boating activity, adequate water flow, and proximity to natural reefs in this developed coastal habitat. •Oysters settled at greater densities in locations with high boating activity.•Hydrology of boating channel favored recruitment in shallow coastal environment.•Adult reefs increased oyster recruitment and deterred barnacle competitors.•Anchored substrate prevented dislodgement of young oysters by boat wakes.•Ideal sites for oyster restoration may overlap with regions optimized for boating.