Assessment of recent eastern oyster (Crassostrea virginica) reef restoration projects in the Great Bay Estuary, New Hampshire: Planning for the future

Current oyster populations in New Hampshire total less than 10% of what they were in the 1980s, and the causal factors for the declines include disease, sedimentation, and human harvest. The two major results from a population ecology perspective have been dramatic losses of oyster shell (the major substrate on which oyster larvae typically settle) as well as juvenile annual recruitment to the remaining reefs. Experimental scale oyster restoration projects addressing these two limitations (substrate and natural recruitment) were initiated in the state in the early 2000s by scientists at the University of New Hampshire (UNH). Since the mid-2000s, the focus has been on full restoration-scale projects, and beginning in 2009 most projects have been collaborative efforts by UNH and The Nature Conservancy (TNC). The present study assessed nine recent collaborative efforts, and provided a comprehensive assessment of restoration success with the goal of determining how the restoration process might be improved

Experimental Quantification of Nutrient Bioextracti on Potential of Oysters in Estuarine Waters of New Hampshire

This project was a short-term field experiment conducted in summer 2010 and designed to provide preliminary data on the bioextraction (removal) of carbon (C) and nitrogen (N) for two different size classes (both \u3c76mm shell height) of eastern oysters (Crassostrea virginica) at six sites in the Great Bay estuarine system in New Hampshire. Sites were chosen to represent a range of ambient nutrient concentrations, water flow conditions, and location within the estuary. Two of the sites were at oyster aquaculture farms: Granite State Shellfish at the mouth of the Oyster River, and Little Bay Oyster Company near Fox Point in Little Bay. At each site, oysters were deployed in 10mm mesh polyethylene bags typically used on oyster farms in New England. Approximately one thousand “seed” size (10?15 mm shell height), or two hundred (200) 1?year old (30?40 mm shell height) oysters were placed into each bag. Two bags (one for each size class) were suspended 10?20 cm off the bottom attached to plastic coated wire cages at each site from August 9 until November 4, 2010. The oysters were inspected and the bags were cleaned each month to reduce fouling. There were no significant differences in final size among the six sites, indicating similar growth rates. Soft tissue %C and %N values, however, varied substantially and significantly (ANOVA, P\u3c0.05) among the sites. Tukey tests indicated significantly higher %C and %N at the Squamscott River (SQ) site, and significantly lower at the Little Bay Oyster (LBO) farm site, compared to the other sites. The ranges of mean soft tissue %C and %N were, respectively, 26.9 to 47.2 and 4.7 to 10.6. Because shell material was not analyzed in the present study, literature values for shell were combined with soft tissue data from the present study to arrive at total whole animal C and N content. Oysters with mean shell height of 35.7 mm contained 0.6 g of C and 0.01 g of N; oysters with mean shell height of 55.6 mm contained 3.1 g of C and 0.07 g of N. Preliminary calculations indicated that if 20 0 acres of bottom area were in full farm production, the annual N removal from the estuary from oyster harvest alone would be 12.56 tons. It is emphasized that the present study represents only the first step in characterizing the nutrient (focusing on N) bioextraction potential for oyster farming in New Hampshire

Stormwater Management Database for the City of Dover, New Hampshire

The overall goal of the project was to make a significant contribution to the Piscataqua Region Estuaries Partnership goal of increasing oyster (Crassostrea virginica) bottom in New Hampshire, and to do so using methods that positively affect multiple species. The focus was on those organisms (mainly macroalgae, invertebrates, and fish) that spend most of their time on oyster reefs—the resident species. A 0.5 hectare (1.25 acres) area was restored in August 2007 by constructing twelve mini-reefs (each ~6 m in diameter) in an area protected from harvest using spat-on-shell (“spat seeding”) from remotely set larvae. There was a consistent trend over time of higher oyster densities on the mini-reefs and on the natural reef within the protected area compared to the adjacent unprotected natural reef. At the end of the project period (1.8 years post-construction of the mini-reefs), total oyster densities in the overall restoration area were about 26% higher than the adjacent unprotected reef. The constructed mini-reefs also consistently had higher total densities and biomass of resident animals, which consisted mainly of invertebrates (only one fish was captured over the entire study), compared to the other reef areas. A total of 15 species of invertebrates were collected from the mini-reefs compared to 10 and 11 species, respectively, from the natural reef in the restored area and the natural reef in the harvested area. The resident (attached) macroalgae community patterns over time indicated higher biomass on the mini-reefs and the protected natural reefs compared to the unprotected reef area on most sampling dates, though there was typically wide variability among replicates. Macroalgal taxonomic richness was similar in all three areas, and there was a total of fourteen species collected from the three areas. Overall, the project resulted in enhancement of oyster reef habitat within the 0.5 hectare restoration area, and characterized the substantial value of oyster reefs in providing habitat for a variety of plant and animal species

2016 Oyster Reef Restoration Project Funded by the Aquatic Resources Mitigation Program

This report describes the results of the construction and initial monitoring phase of an oyster restoration project conducted in 2016 by the University of New Hampshire (UNH) and The Nature Conservancy (TNC), funded by the New Hampshire Aquatic Resources Mitigation Program. The overall goal of the project was to construct 5 acres of new oyster reef habitat in an area adjacent to a live natural reef northwest of Nannie Island, in the Town of Newington, NH, off Woodman Point. The report is organized according to the four major tasks listed as deliverables in the subaward to UNH from TNC

Video-Based Mapping of Oyster Bottom in the Upper Piscataqua River, Sturgeon Creek, and Spruce Creek

Towed, underwater videography was used to map and characterize the extent of oyster bottom in the upper Piscataqua River, Sturgeon Creek, and Spruce Creek. Georeferenced video imagery was obtained on five different days in summer and fall 2008. Significant shell bottom (with live oysters in most areas) was found only in the upper Piscataqua River in two areas: (1) the general location of the previously mapped (2003) upper Piscataqua River reef, and (2) in the Piscataqua River at the mouth of Sturgeon Creek. The Sturgeon Creek reef was classified into low and high density shell which covered a total area of 15.6 acres (~63,000 m2). Recommendations included additional survey work in the lower Salmon Falls and Cocheco Rivers, and Spruce Creek

Oyster Bed Mapping in the Great Bay Estuary, 2012-2013

Six major oyster beds (reefs) in New Hampshire are mapped periodically to assess wild oyster populations in the Great Bay Estuary. Data on the spatial extent of the beds are combined with density and other measures to estimate the abundances of live oysters. The first objective of the present project was to determine the spatial extent of these six oyster beds, and to compare the 2012/2013 data with previous mapping efforts. A second objective was twofold: to map the extent of live oyster bottom at selected recent oyster restoration sites, and to map areas where oyster beds have been known to occur historically but not recently. Towed underwater video methods, as used in previous oyster mapping efforts in New Hampshire, were used for this project. All recorded video was classified into three categories: ”reef” (\u3e20% shell cover and live oysters visible); ”sparse shell” ( Two of the natural beds (Nannie Island [2012: 32.4 ac] and Oyster River [2012: 1.6 ac]) had similar total bottom area coverage compared to most previous mapping efforts. Three beds (Adams Point [2012: 15.9 ac], Squamscott River [2012: 7.7 ac] and Woodman Point [2012: 15.4 ac]) had substantially greater area coverage compared to previous surveys. In all three cases, however, the increases were likely due to additional adjacent areas being surveyed. In contrast to the others, the Piscataqua River bed appears to have substantially decreased in bottom area coverage (2012: 7.0 ac) compared to previous surveys. Selected oyster restoration sites were also video surveyed in 2013 to determine bottom area coverage that could be considered “reef” and therefore considered as part of the overall oyster resource in New Hampshire. Restoration sites in the Lamprey River, Oyster River (3 sites), and at Fox Point in Little Bay were imaged. Due to poor image quality, full bottom area coverage could not be determined for any of the sites. Nonetheless, substantial areas of at least “sparse shell” bottom, and live oysters in some areas were recorded at all sites. These restoration sites as well as additional sites are scheduled for video surveying and quantitative sampling in 2013. The third focus of the project was to survey areas where oyster beds historically occurred. Of the four general areas surveyed, live oyster reefs were found in two areas: Lamprey River (0.9 ac) and mid-Great Bay (35.2 ac). In sum, these two areas represent a major addition to the known live oyster bottom in the state. Moreover, these findings strongly suggest that live oyster reefs may be in other areas where oysters have not been known to exist in recent years. Overall, this project has added substantially to our knowledge of where live oysters occur in New Hampshire as well as the total bottom area coverage. A total of 120 acres of bottom area classified as “reef” was mapped. Additionally, the extent (perhaps 100 ac or more) of bottom area that had sparse shell but apparently few or no live oysters in mid-Great Bay bed and in the Nannie Island/Woodman Point area is important because these areas represent excellent oyster restoration opportunities. However, they will need to be mapped in more detail to sufficiently design future projects

Restoring Native Oysters in Great Bay Estuary, NH (2011)

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 \u3e200K 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 \u3e500K 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