Effects of Location and Hand Harvest of Intertidal Oyster (Crassostrea virginica) Reefs on Oyster Populations and Habitat Characteristics

Centuries of anthropogenic pressures, in particular harvesting, have reduced eastern oyster (Crassostrea virginica) populations throughout the eastern coast of North America. Harvesting oyster reefs can affect reef structure and oyster populations by reducing complexity and removing reproductive individuals and their shells, which are important for larval settlement. Although numerous studies have investigated the effects of tonging and dredging on subtidal oyster reefs, the effects of hand harvesting on intertidal reefs are not well-documented. Intertidal reefs in the Tolomato, Matanzas, and Salt Run estuaries in Northeast Florida were sampled during 2015–2016 to investigate differences in oyster population and reef structure inside and outside commercial/recreational harvest areas. We hypothesized that live oyster density, oyster clusters, mussel density, and amount of cultch would be lower in open harvest areas compared with closed harvest areas. In Salt Run, the estuary region with the greatest assumed harvest pressure, all metrics were lower in open harvest areas than in closed areas. In addition, oysters on reefs in closed areas contained greater proportions of juvenile oysters compared with reefs in open areas, indicating less recruitment on harvested reefs in Salt Run. Patterns between open and closed harvest areas in two other regions of the estuary (Tolomato and Matanzas Rivers) were less consistent, perhaps due to less concentrated harvest pressure or the influence of other stressors in those regions. These comparative results suggest that hand harvesting can affect intertidal oyster reef habitat and population structure, and that the amount of harvesting may play a vital role in determining the extent of the effects. Determining how these effects are related to the long-term sustainability of the resource is an important next step.