Bringing Oysters Back to NH’s Great Bay

"COLSA research team leads the charge on regional efforts to restore native oyster reefs in New Hampshire 

Krystin Ward, a laboratory research supervisor at the UNH College of Life Sciences and Agriculture, navigates a small skiff from the pier at UNH’s Jackson Estuarine Laboratory, heading southward in New Hampshire’s expansive Great Bay Estuary. Piloting the boat across choppy, dark water and beneath a gray sky, she talks about working in oyster reef restoration in Great Bay — supporting the efforts of UNH Professor of Biological Sciences Ray Grizzle — and the beginnings of her own oyster farm, Choice Oysters, in 2011. She discusses the long-term collaborative effort to restore the bay’s oyster reefs, which covered as many as 1,000 acres in the 1970s but have gradually dwindled. Based on aerial surveying conducted in 2020, live natural oyster reefs now cover approximately 80 acres of New Hampshire’s Great Bay. 

“When I began at UNH in 2005, Ray had already been doing oyster reef restoration in the bay for five years,” Ward says. “In 2009, we partnered with some major organizations, including the USDA’s Natural Resources Conservation Service (NRCS/USDA) and The Nature Conservancy (TNC), to really grow these efforts and to use a barge every summer to deposit several tons of oyster and clam shells on or near depleted beds, building them up so that oyster larvae will set and grow upon them.” 

On this day, Ward and her sister (and fellow oyster farmer), Laura Brown, are checking on efforts by Riverside & Pickering Marine Contractors to deposit about 450 cubic yards of shells that have been stored and dried for at least 6 months to remove any remaining tissue near Nannie Island, situated just off the Great Bay National Wildlife Refuge in Newington, New Hampshire. The Nannie Island reef restoration project, which is being funded by the NRCS/USDA, has been ongoing since the 15-acre reef was closed toshellfish harvesting in2021. From2016to2021, Ward and Grizzle observed a nearly 90 percent reduction in the natural oyster reef at Nannie Island. However, by adding new beds and farmed oysters tothesite,they’rehopingtheeffortwilljumpstartthe area’s native oyster population. 

More Than Two Decades of Great Bay Oyster Restoration Efforts 

“Our goal here, at Nannie Island, and at our restorationsiteatthemouthoftheSquamscottRiver, is ultimately to get more oyster larvae into the water column and provide new substrate for the larvae to set upon,” Ward says. “We deposit the shell in early summer so that when the oysters begin breeding as the water warms — usually about July-August — the larvae they produce will have new area to set upon.” 

Once the shells are added to the Nannie Island reef, another 50 cubic yards will be deposited at a restoration site near the mouth of the Squamscott River. In previous years, Ward and Grizzle led restoration efforts at the mouth of the Lamprey River, where they were able to grow the existing natural reef further up into the river. 

“By working in these same areas, we can concentrate the shell substrate in a smaller region, creating deeper beds, instead of just fanning thinner layers of shell out over several acres,” says Ward. “Sedimentation can be a problem, but by putting the shell about a half foot from the floor, we can establish a good layer and make a big difference.” 

And they’re already seeing that difference — both from large-scale deposits like the one at the Nannie Island reef and from smaller deployments of farmed oysters from farms in Great Bay Estuary’s Little Bay. Using underwater cameras, Ward and Grizzle monitor both the reef growth and the addition of new spat and juvenile oysters. The cameras allow them to know when an area has a good, solid substrate in place, and when the oysters in the area begin reproducing and growing the reef naturally by attaching and settling upon one another. 

“For the Nannie Island reef, we’re beginning to see more spat settling on the living oysters, indicating that they’re growing the reef naturally,” Ward says. “If this trend continues, we’re hopeful that the oyster population may rebound and some of this area will be open to recreational harvest again.” 

“A major step forward came as result of COVID when we were able to secure funding to purchase live oysters that couldn’t be sold by the local farmers because restaurants were largely closed,” explains Grizzle. “We have added those live oysters to reef sites and the results so far have been encouraging, mainly because the farmed oysters have higher survival rates and we’ve found greater concentration of spat in the areas where they’ve been deployed.” 

“So partnering with local oyster farmers in the restoration of Great Bay’s wild oyster populations has been a critical step forward in these efforts,” he added. 

How Oyster Farming Encourages Great Bay Restoration 

Laura Brown, who’s owned and operated Fox Point Oysters in Great Bay Estuary’s Little Bay since 2012, says that farming oysters and helping conserve oysters in Great Bay are two concepts closely connected, and one can’t really be done without the other. 

“I don’t think you can be an oyster farmer in this area without being an environmentalist to some degree too,” says Brown. “Being involved in the restoration effort has been a goal of mine over the years and one that I’m excited to pursue more now.” 

Just the influx in oyster farms in Great Bay over the past decade have contributed to restoration efforts and increased biodiversity, says Ward. 

“If you’re putting shell on the bottom, that’s creating a natural reef and building habitat for fish and other invertebrates — so you’ll see a lot more biodiversity in a reef structure than you would on a mudflat,” she adds. “Through research, we’ve found that even the oyster farms in Little Bay are acting like reefs and supporting greater diversity. It’s really neat to think about the impacts of local oyster farms toward supporting the overall health of Great Bay and its many tributaries.” "