A new study supplies more evidence that oyster restoration efforts are having the desired impact in Maryland’s tidal rivers, forming better reefs than those set aside as sanctuaries or regularly maintained for commercial harvests.

SERC oyster bottom survey

Biologists with the Smithsonian Environmental Research Center used underwater cameras to survey oyster reefs, including the one shown here in Maryland’s Tred Avon River. 

The differences are visible to the naked eye — or, in this case, the camera lens. For the first time, researchers used videos and photos to analyze a broad swath of the bottom habitat.

The methods aren’t intended to replace the labor-intensive diving and tonging techniques for surveying the Chesapeake Bay’s oyster population, according to the study’s authors. But they say their approach can be useful for obtaining a reef’s “qualitative” attributes at a fraction of the time and cost.

“It’s a really easy, fast method to go out and keep a tally on how the reefs are doing,” said Keira Heggie, lead author of the study and a technician at the Smithsonian Environmental Research Center in Edgewater, MD.

Heggie and her research partner, Matthew Ogburn, assigned a score from zero to three to each of the 200 submerged sites they surveyed on Maryland’s Eastern Shore. Higher scores were given to reefs with more height and broader oyster coverage along the sandy bottom.

“You basically just need a camera you can drop to the bottom and take a little picture, maybe a bit of video, and in a few seconds decide which category [the reefs] fit in,” said Ogburn, a senior scientist at SERC. “It doesn’t provide incredibly detailed information, but it allows you to survey a lot of sites really quickly.”

The study adds to the growing evidence in the Chesapeake region that actively restored reefs are thriving while their unrestored counterparts continue to lag.

In Harris Creek, the only tributary in the study where oyster restoration had been completed at the time, nearly 75% of the restored sites scored a three on the researchers’ scale. Although the unrestored reefs in the creek are also protected by a harvesting ban, none of them mustered a three.

“Restoration was effective and working in the many ways it was intended,” Ogburn said. “There are a lot more oysters there. There’s a lot more structure. It looks like there’s a lot more vertical habitat, so it doesn’t get sedimented over. It looks like it could last well into the future.”

Maryland’s current oyster management policy dates to 2010, when 9,000 acres of the “best” remaining oyster bars were designated off-limits to harvest. The other 27,000 acres’ worth of productive oyster habitat remained in the public fishery.

Under the 2014 Chesapeake Bay Watershed Agreement, Maryland and Virginia pledged large-scale oyster restoration efforts in five waterways each. Maryland has selected three tributaries of the Choptank River — Harris Creek, the Little Choptank River and the Tred Avon River — as well as the Manokin River in Somerset County and St. Mary’s River in St. Mary’s County.

The Smithsonian paper was published the journal Marine Ecology Progress Series I in June, arriving at another inflection point in Maryland’s oyster strategy. A state law passed in 2020 requires a more consensus-based approach to managing the bivalves, which are at a fraction of their historic population. The law set a deadline of this Dec. 1 for the Oyster Advisory Commission to deliver its final report.

One of the biggest questions is what will become of the sanctuaries where no restoration has taken place but harvesting remains barred. Commercial watermen have long been skeptical of their ecological benefits, arguing that regular dredging would keep the bars from getting covered in sediment.

“It doesn’t seem like the sanctuaries are doing much of anything,” Robert Newberry, head of the Delmarva Fisheries Association, told the commission in May.

For their part, Heggie and Ogburn surveyed four streams: The Little Choptank, Harris Creek, the Tred Avon and Broad Creek (another Choptank tributary). In each, the researchers randomly studied 25 sites on restored reefs — including both sanctuaries and harvested areas — and another 25 on unrestored reefs designated as no-harvest sanctuaries.

The survey was conducted in November 2017, about two years after the 348-acre Harris Creek restoration was completed. The 358-acre Little Choptank restoration wasn’t completed until last summer. The 130-acre Tred Avon restoration is scheduled to be wrapped up this year.

Harris Creek scored a 3 at 40% of its sites, with almost all of the high scores coming on restored reefs. There was a steep drop-off after that. The Little Choptank’s reefs received a score of 3 at only 14% of its sites. The Tred Avon got top marks at 6% of sites, followed by Broad Creek (a heavily harvested tributary) at 2%.

Ogburn cautioned against interpreting his study as proof that unrestored sanctuaries aren’t working. When they were set aside, only 26% of the so-called “best bar” area was included in them, well below the state’s 50% goal, according to a Maryland Department of Natural Resources assessment.

“It’s like planting corn in a desert and expecting it to grow,” Ogburn said.

Ogburn said the findings suggest that more investment is needed to restore the state’s oyster sanctuaries. An oyster reef monitoring report issued by the state-federal Chesapeake Bay Program’s oyster in December showed that a “wide majority” of restored reefs were meeting their goals. On a much smaller scale, the new study confirms such conclusions, he said.

But his survey was much easier and faster to conduct than its predecessors. The protocol is simple. Researchers lower three GoPro cameras mounted on a PVC pipe frame into the water. Two cameras are aimed horizontally for shooting continuous video while one is pointed directly below and only shooting photographs of the bottom. After two minutes, researchers haul it back aboard the boat and motor off to their next site.

A two-person team, they found, was able to capture 50 videos in a day — about five or six times the amount that can be covered by a dive teams or a tong survey.

Ogburn and Heggie conducted a wide survey using the same methods in 2019 and 2020 in all 10 oyster restoration waterways in Maryland and Virginia and are analyzing the results for a future paper.

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