Hydrodynamics, elevation, and restoration history structure intertidal oyster recruitment

Reversing global declines of foundation species requires recovery of critical bottlenecks in population dynamics, particularly the recruitment of early life stages. Understanding the controls on recruitment can substantially improve restoration success. We investigated how geophysical conditions and restoration history determine recruitment in eastern oysters (Crassostrea virginica), a foundation species requiring substantial restoration efforts following severe, widespread losses. Over 3 years, we measured annual oyster recruitment to standardized ceramic tiles on 9–16 intertidal reefs in coastal Virginia, USA. We paired these measurements with an 18-year time series of recruitment to natural substrate on 8 natural reference reefs and 44 restored reefs (0–16 years post-construction). Recruitment to tiles was highly correlated with recruitment to natural substrate, validating our methodology. Recruitment was positively spatially autocorrelated within 1 km and increased 9–14 × with moderate wind fetch. A one-meter increase in substrate elevation tripled recruitment. Recruitment was 4 × higher on natural reefs compared to restored reefs, regardless of elapsed time since restoration. Geospatial model predictions identified 6% (24 km2) of intertidal areas as highly suitable for oyster recruitment, offering a refined target for restoration practitioners. By integrating multi-year field studies, long-term monitoring, and habitat suitability modeling, our research identified environmental conditions favorable for oyster recruitment, offering insights that could enhance restoration planning and population resilience. Our findings provide actionable insights for optimizing oyster restoration by targeting areas with favorable wind fetch and elevation. These results offer valuable guidance for spatial planning in restoration and may inform strategies for other species where recruitment limits restoration success.