Oyster Reef Habitat Restoration: Relationships Between Oyster Abundance and Community Development based on Two Studies in Virginia and South Carolina

Most Atlantic and Gulf coast U.S. states with an oyster fishery have operated some form of oyoter reef enhancement program over the past 50 years. Although programs were initially only directed at oyster fisheries augmentation, recent emphasis has shifted to include the restoration of their ecological functions. Furthermore, many of these programs are managed by environmental organizations or state agencies not traditionally involved in fisheries management or research, but rather in ecological restoration, monitoring, and/or environmental education. A simple assessment of shellfish meetings over the past five years, including the inaugural Restore America's Estuaries meeting from which this paper is derived, revealed more than 300 presentations related to oyster restoration, with fewer than 25% focused solely on oyster fishery restoration. Unfortunately, many of those efforts lacked well-defined "success criteria," with progress often judged using fisheries-based metrics ouch as market-sized (generally 75 mm or 3") oysters. Here we discuss our findings as they relate to the value of alterative restoration metrics and associated success criteria using data from two very different systems and approaches: one conducted in Virginia's lower Chesapeake Bay (Rappahannock River), based on data from a two-year program utilizing oubtidally constructed reefs of different reef "scale," and the other a long-term study in South Carolna focusing on intertidal reefs. For each system, we compared newly created reef structures, relating oyster abundance and size to resident species abundance and biodiversity over time. Our results revealed positive correlations between several community descriptors and the size and density of oysters on the reefs. Of the 15 significant (and b marginaly insignificant) correlations observed out of a total of 78 examined across both studies, al but one were positive. The exception was for epifaunal invertebrate diversity vs. oyster biomass on the Rappahannock reefs. Despite these numnerous positive correlations, none indicated that market-sized oysters are a prerequisite for supporting an abundant and diverse community. For example, intertidal oysters >75 mm in South Carolina typically make up <10% of all reef oysters, with a maximnum of 18%. Finally, until we have a more thorough understanding of the interactions between individual species and the mechanisms linking oyster populations and reef community attributes, we propose that oyster abundancelsize structure be used for assessments. Future studies need to develop and evaluate restoration progress using a combination of standardized criteria that can be applied to reef success over a wide geographical range and surrogate or indirect ecological measures (eg., filtering, habitat use)