As TNC restores floodplain on the Roanoke River and works to improve flows on the Cape Fear River, some things are visible. You can see more natural water flows on the Roanoke. You can see pulses of water released from Jordan Lake into the Cape Fear. But is that work helping rare and endangered fish? Thanks to new technology, we have the answer.
Environmental DNA (eDNA) works on the same principles as the genealogical tests many of us take or to use a pop culture reference, it is kind of like the television crime procedural where the guilty party is outed by DNA collected at the crime scene. Water samples are collected and sent to a lab, where it can be determined if a particular fish species swam there recently.
Aaron McCall has worked for TNC for nearly 24 years. “When I first started working here, I got my first email address. We were still penciling in our time sheets and faxing them,” he remembers. “I still had a regular camera and handheld GPS units weren’t very accurate.”
Up until a few years ago, Aaron would have had to put up gill nets to see if rare fish were frequenting restored floodplain on the Roanoke. “Gill nets actually end up killing many fish,” he says. “You gets lots of bycatch other than the fish you are looking for.”
“We know that these work will open up floodplains and help with water movement, but at TNC we are also concerned about biodiversity—trying to help rare and endangered species,” says Water Program Director Julie DeMeester. “Blueback herring are so rare that there is a moratorium on fishing for them. Sturgeon are an endangered species. We are getting DNA hits on those fish in areas where we are trying to improve management. That makes your heart sing.”
In 2022, eDNA showed that blueback herring were present at all of TNC’s floodplain restoration sites on the Roanoke. On the Cape Fear, it showed a sturgeon swimming well past the first lock and dam on the river, something that hadn’t happened in at least a decade. It coincided with a pulse of water released from Jordan Lake, which was supposed to help the migratory fish swim past the lock and dam to their spawning area.
McCall says he is using the eDNA results for education. He made a presentation to the hunt club that owns the Roanoke River restoration site. “They could see the water coming in and out of the floodplain at a more natural rate,” he says. “But, actually showing them that the blueback herring are there, that’s important. They know that blueback herring are a food source for stripers, and they like to catch the stripers.”
The eDNA work is financed by the National Oceanic and Atmospheric Administration and the U.S. Army of Corps of Engineers. While the results are important for North Carolina, they can also benefit the country. “The Army Corps of Engineers invested in this project because they want to find out how eDNA can be a tool to help them better manage river flows,” says DeMeester. “The more we can show that this technology and this is tool is useful, then we are helping the largest water manager in the country.”
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