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By Sarah Wheeler

MOREHEAD CITY — UNC-Chapel Hill biologists tagged and released two red drum at the same location in the New River estuary on the same day. A year later, the fish were 450 miles apart – one within 3 miles of the release site and the other in Delaware.

That two fish of the same species would act so differently surprised Joel Fodrie, a biologist at the UNC-Chapel Hill Institute of Marine Sciences and lead scientist on a project to study the movement of red drum and black drum, two species prized by recreational and commercial fishermen.

To help him study drum, Fodrie has enlisted the help of local anglers to meet his goal of tagging and tracking 90 fish. The Onslow County Chapter of the Coastal Conservation Association and the Sturgeon City Environmental Education Center in Jacksonville made the partnership possible.

Over the years, anglers who belong to the Coastal Conservation Association have noticed that they rarely catch fish in the middle size range of 30 to 40 inches.

“We were wondering where these fish go between these size ranges,” said Rocky Carter, state vice president of the Coastal Conservation Association. “Maybe by being involved in the project, we can unlock the secrets of their life cycles.”

Understanding fish movement and behaviors underlies most fisheries management decisions and stock assessments, but tracking fish is a big challenge for scientists. North Carolina spends hundreds of thousands of dollars each year restoring reef habitat, but calculating the benefit to fisheries requires information on how fish use it.

Fodrie seeks to fill this gap through his research, funded by the N.C. Coastal Recreational Fishing License Program.

Since 2012, Fodrie and his team of scientists have used acoustic tagging techniques to study the movement of red drum and black drum living in the New River estuary near Jacksonville. Scientists surgically implant acoustic tags, which emit encoded sound signals to hydrophone receivers within 1 kilometer. The surgery lasts roughly 20 minutes. All fish receive anesthesia and fully recover within three weeks.

Each tag reveals a hidden story of where a fish calls home and where it has traveled over tag’s 15-month battery life.

Hydrophones scattered throughout New River Estuary record a unique data “ping” as fish swim by. Scientists lined some of the hydrophones across a narrow channel in the estuary to detect fish that emigrate to new areas or leave and return. Scientists also placed hydrophones in different habitats to illustrate how fish utilize enhanced oyster reef sites and artificial reefs compared with sandy non-restored habitat.

“We now have 80 hydrophones in the water,” Fodrie said. “Our hydrophone density is probably higher than any effort.”

The early results indicate black drum prefer artificial reefs over non-restored habitat or enhanced sites and that red drum do not appear to have any preferences. Fodrie also found that some fish remained in the estuary while others emigrated and traveled long distances, activating hydrophones in other states. These fish often returned to the exact creek from which they emigrated.

“They seem to know their neighborhood and return to it frequently,” said Fodrie.

Fruitful collaboration

So far, the collaboration between scientists and fishermen has proven advantageous, with several fish caught by volunteer anglers. The partnership also serves as a platform for biologists and fishermen to share what they know. Fodrie’s lab manager, Matthew Kenworthy, has shared data with volunteer anglers interested in fish movement and hot spots for fishing.

Carter predicted his tagged fish would “get comfortable” in an area. But his perspective changed when he saw the fish detected at multiple locations in the estuary, both up and down stream. Carter now thinks fish may respond to changes in water quality after storms, moving closer to the ocean as salinity in the estuary drops.

Fodrie has suspected that storms and water quality affect red drum movement for quite some time. He is partnering with Hans Paerl, a UNC-Chapel Hill marine and environmental science professor who has water quality sensors throughout the estuary. These sensors will help determine how fish respond to changes in water quality and salinity after storms.

Scientists plan to present results to the Coastal Conservation Association and the New River Roundtable, a group of stakeholders engaged in river stewardship.

The research addresses multiple management goals of the state Division of Marine Fisheries, including quantifying the success of restoration efforts. Scientists and fisheries managers will use the data to identify emigrating and resident fish stocks.

“We all can benefit from what the scientists are doing,” said Carter, who hopes to strengthen communication between scientists and fishermen through research. “We want to preserve these fish.”

Wheeler: 919-829-8994 Twitter: @sarahgwheeler