Restoring Oyster Populations in Great Bay | Conservation Law Foundation

Restoring Oyster Populations in Great Bay

Peter Wellenberger

One man's waste makes another oyster's spawning bed: tons of recycled shells are spread from a barge in the Squamscott River to restore an oyster reef. Photo courtesy of R. Konisky, TNC

Most people don’t realize that oysters are only found in estuaries. At one time, oysters thrived throughout the Great Bay estuary and were highly desired for human consumption. Because oysters filter the water to feed, they also help to remove pollutants and nutrients and play an important role in keeping our estuaries clean.

Unfortunately, it is increasingly difficult to find oysters in the Great Bay estuary due to disease and siltation. In the mid-1990s, the introduction of two parasitic protozoans – Dermo and MSX – caused a large-scale die-off of adult oysters.  Since then habitat changes due to excess siltation from numerous storm events – an impact of Climate Change – has furthered reduced populations. Forty years ago, there were approximately one thousand acres of oysters in the estuary; today, that number is closer to 70 acres.

To help reverse this decline, The Nature Conservancy and the University of New Hampshire have been working to restore populations by building new oyster reefs in the tidal rivers. Reefs are constructed by spreading tons of recycled shells as oyster spawn need a hard surface to settle on. Once in place, seed oysters are added with the hope they will survive and mature to adults.

After working in the Oyster and Lamprey rivers, the Squamscott River is now being targeted. This effort will build upon an existing reef that extends from the railroad trestle towards Great Bay. Working off a barge, crews recently spread 75 ton of recycled shell in hopes of establishing a two acre reef. Some of the recycled shell is from local restaurants collected by the Coastal Conservation Association-NH Chapter, another partner in the project.

Ray Grizzle at the UNH Jackson Estuarine Lab has been testing different brood stocks and general oyster restoration methods to determine how best to move forward. “During 2012, we hope to be able to conduct in collaboration with EPA scientists a comprehensive assessment of all the major restoration sites we have worked on since 2000. The aim of this effort will be to better determine what has worked and what hasn’t so we can improve the design – and the success – of future projects.”

Support for this year’s restoration project comes from several sources, including federal grants and State of NH Moose Plate funds. CLF and TNC have also been working together to make oyster restoration part of a recent settlement between EPA and Grimmel Industries.

For years, the massive scrap metal facility owned by Grimmel has discharged heavily contaminated stormwater into the Piscataqua River. As a direct result of CLF’s advocacy, the facility has been required to implement significant upgrades to address toxic stormwater pollution runoff into the Piscataqua River. During EPA’s enforcement process, CLF urged EPA and Grimmel to develop a Supplemental Environmental Project to restore oyster and eelgrass habitat in the estuary and worked with Ray Konisky of TNC to develop a restoration proposal. EPA embraced the approach, leading to a commitment by Grimmel to fund an oyster and eelgrass restoration project next year.

While any new oyster reef is a welcome addition, the health of the estuary continues to decline from nitrogen pollution. By filtering the water, oysters are an effective nitrogen-reducing agent. However, they are only a small part of the solution and much more needs to be done such as upgrading local wastewater treatment plants and reducing the amount of stormwater entering the estuary.


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