Cooperative Fish and Wildlife Research Units Program: all
Education, Research and Technical Assistance for Managing Our Natural Resources

AAcross coastal areas of the U.S. Gulf of Mexico, the Deepwater Horizon oil spill resulted in significant ecological injury and over 8 billion USD directed to restoration activities. Oyster restoration projects were implemented with regional goals of restoring oyster abundance, spawning stock, and population resilience. Measuring regional or large-scale ecosystem restoration outcomes challenges traditional project-specific monitoring and outcome reporting. We examined the outcomes of oyster restoration at the project-level and discuss potential pathways to measure progress toward region-level goals. An estimated 15 km² of oyster habitat was restored across 11 different estuaries with 62 individual reef footprints created, ranging in size from ~ 0.2 to >1.45 km². Individual sites were distributed across the salinity gradient, and all reefs were subtidal. One-year post-restoration, mean total oyster density across all sites was 53.0 ± 60.7 ind m^-2 of which 38.4 ± 42.2 ind m^-2 were adult (> 25 mm shell height) oysters. Recent data available for all sites indicates reduced densities of total oysters (44.6 ± 70.9 ind m^-2) and adult oysters (14.6 ± 21.6 ind m^-2). These data provide insight into project specific outcomes, suggesting an overall enhancement in oyster abundance from restoration, but fall short of informing outcomes at the regional level that incorporate cumulative effects on adjacent and connected reef populations, or resiliency of the regional oyster resource. Developing outcome measures that incorporate cumulative and synergistic impacts of individual projects will require reconciliation and consideration of project-level planning and monitoring performance targets with broader spatial and temporal monitoring requirements.