PREP Reports & Publications


The eastern oyster (Crassostrea virginica) in New Hampshire’s Great Bay Estuary has declined in the past decades, with local populations at very low densities due primarily to disease, excessive siltation, and past over-harvest. The loss of filtering oysters results in diminished ecological benefits for water quality, nitrogen control, and other services that healthy oyster populations provide. In support of regional management objectives to restore millions of oysters to the estuary, the Nature Conservancy (TNC) and the University of New Hampshire (UNH) piloted and scaled-up methods to successfully rebuild oyster reefs. Based on pilot results in 2009, we developed a technique using a thin layer of recycled clamshell “planted” over silted channel bottom as a hard substrate foundation to recruit natural spawn, supplemented with hatchery-raised and volunteer-grown seed “spat”. In 2010, a full acre reef was constructed and seeded at the mouth of the Oyster River in Durham, producing a one-year standing stock of >200K oysters. In 2011, restoration efforts were scaled up significantly, led by support from the Piscataqua Region Estuaries Partnership (PREP), with two acres of reef construction at the mouth of the Lamprey River (Newmarket NH). In June 2011, approximately 200 yd3 of seasoned surf clam shell was deployed at the site for total shell coverage of 80,000 ft2 (7,432 m2). Fall monitoring results showed that an estimated 58K oyster spat were recruited to the reef (19.5 spat/m2). Supplements from UNH remote setting operations added 428K spat to the reef areas, plus an additional 17K spat were raised by community volunteers. By fall 2011, the completed reefs achieved a standing stock of >500K oysters. In addition, another half-acre restoration site was built nearby with farmer support. Collectively, our efforts demonstrate significant progress towards a regional goal of 20 acres of oyster reef restored by 2020, and position us for further expansion of restoration work going forward.


Piscataqua Region Estuaries Partnership

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Piscataqua Region Estuaries Partnership

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