Oyster Restoration

How many acres of oyster restoration have been initiated?

More than 26 acres of oyster restoration have been initiated since 2000—15.5 of those acres since 2011. Sedimentation hampers success at most but not all sites.


The oyster fishery and commercial oyster aquaculture industry support the local economy through jobs and sales. Filter feeding oysters can improve light penetration through the water; they provide critical habitat for many species of invertebrates and juvenile fish and they can sequester nitrogen and carbon. Unfortunately, the Great Bay Estuary has lost 89% of its wild oysters since 1993, which results in less available substrate and, in turn, less available area for juvenile oyster spat to settle.
Restore 20 acres of oyster reef habitat by 2020.
10.8 acres of oyster restoration was initiated between 2000 and 2012. Between 2012 and 2016, an additional 15.5 acres of oyster restoration were established in the Great Bay Estuary (Figures 19.1 and 19.2) through collaborations between the University of New Hampshire (UNH) and The Nature Conservancy (TNC). The cumulative total for oyster restoration sites is now over 26 acres, above the PREP goal of 20 acres. Although 26 acres of restoration area exist, each site is only partially covered by oyster shell. For example, a common design is to establish multiple small circles of shell for oysters to settle on.

Unfortunately, in many cases, these restoration sites have struggled to remain viable, primarily due to burial by fine sediments (sedimentation).60 Table 19.1 shows monitoring results for seven different restoration sites; in four of the seven sites, shell cover has decreased since initial construction. Only one site showed an increase in shell cover.

Monitoring of these sites suggests several keys to successful future restoration, including: 1) build reefs to achieve greater vertical height to guard against burial by sediments and 2) select sites as close as possible to a natural reef. Recent UNH research showed that recruitment (new oyster larvae settling) decreased significantly as distance from a native natural reef increased.61

Oyster aquaculture (i.e., oyster farms) in the Great Bay Estuary has increased steadily since 2011, with 22 aquaculture harvest licenses issued in 2016, as compared to only five in 2011. In 2016, NH Fish and Game estimates that over 180,000 oysters were harvested from aquaculture activities.

Figure 19.1 Map showing major oyster restoration activity. The red dots show general location of sites that have been monitored. Note that two of the red dots show the location of multiple sites (in the Lamprey River and in Great Bay). The blue dot shows the most recent restoration site in the Great Bay.

Figure 19.2 Cumulative acres of oyster restoration projects 2000-2016. Data pertain to the total areas of a restoration site, not necessarily the area covered by oysters.

Table 19.1 Change in shell cover after initial construction.