Oyster reef recovery: Impacts of rotational management and restoration efforts on public fishing grounds.

Coastal ecosystems are degraded worldwide and oyster reefs are among the most threatened coastal habitats. Oysters are a critical ecosystem engineer and valuable fishery species, thus effective management strategies must balance tradeoffs between protecting reef ecosystems and continued human use. Management practices for oysters commonly incorporate shell replenishment (provisioning hard substrates to increase reef relief) and spatial management (rotational harvest areas or sanctuaries); however, the impact of these practices on reef dynamics and fisheries outcomes are poorly understood, particularly on harvested reefs. This project examines the efficacy of shell replenishment and spatial management practices on public fishing grounds by analyzing long term datasets available for the Rappahannock River in the Chesapeake Bay, USA. Using generalized linear mixed effects models, we examine how oyster reef metrics (brown shell substrate L m, recruit density m, market density m) and fisheries efficiency (meeting daily bushel harvest limit or not) respond to management actions. Our results indicate that a 3 y rotation maintains the underlying reef structure, enhances recruitment, and increases market sized oyster density by 1.23 oysters m on average. Sanctuaries and harvested reefs had comparable brown shell and recruit density; however, sanctuaries had higher market oyster density on average. Shell replenishment practices directly enhanced harvester efficiency, particularly in harvest areas with poor reef condition. Our results indicate that low levels of replenishment (∼1000 bushels acre) provide substantial benefits to oyster reefs and the fishery. This study is the first to evaluate the marginal benefits of replenishment activities for biological and fisheries outcomes, and a novel, real world assessment for oyster restoration practices on public fishing grounds. Cumulatively, our findings show that spatial management and replenishment practices enhance oyster reefs in temperate estuaries and offers a framework applicable to other degraded ecosystems worldwide.