Recruitment Enhancement as an Indicator of Oyster Restoration Success in Chesapeake Bay

Abstract

Oyster (Crassostrea virginica) recruitment in Chesapeake Bay, USA, dropped precipitously as stocks declined (1920s–1985), then collapsed (1986–present). Occasional recruitment spikes occurred, driven primarily by seasonal drought. Recruitment spikes helped sustain the fishery at a small, variable level for years post-collapse, as fishers took advantage of these strong year classes. Historically, oyster recruitment was higher, more reliable, and more stock-driven, with weather exerting less, though still significant influence. Analysis of publicly available oyster spat (young juvenile oysters) settlement data revealed the reestablishment of a steadier, historic pattern of oyster settlement and recruitment potential in the Great Wicomico River (GWR), where local stocks have been greatly enhanced by a large sanctuary reef network constructed in 2004. In 2012, an oyster shellstring survey in the GWR revealed the highest mean oyster settlement for any Bay tributary since such surveys began nearly 70 years ago. This unprecedented recruitment enhancement is significantly correlated to the large stock on the sanctuary reefs and a strong indicator of restoration success and longterm sustainability, as these reefs are well past the average age of senescence (five years) for restored reefs. With the expansion of large-scale Eastern oyster restoration efforts in Maryland’s portion of the Chesapeake Bay, developing efforts in the northeastern states of Massachusetts, Connecticut, New York, and New Jersey, and similar efforts to restore the Olympia oyster in the Pacific Northwest (Oregon, Washington, British Columbia), these findings are particularly timely and applicable.