NOAA Fisheries researchers and colleagues captured and tagged leatherback sea turtles off Beaufort, North Carolina May 7-16, continuing a 2017 project to assess abundance, movements, and behavior. It is the first time leatherbacks have been tagged off North Carolina, where they aggregate in coastal waters during their northward spring migration.
Turtle researchers Heather Haas and Eric Matzen from the Northeast Fisheries Science Center (NEFSC)’s Woods Hole Laboratory joined colleagues Chris Sasso and Larisa Avens from the Southeast Fisheries Science Center (SEFSC) and representatives from North Carolina State University (NCSU) College of Veterinary Medicine, North Carolina Wildlife Resources Commission (NCWRC), Coonamessett Farm Foundation (CFF), and the Department of Fisheries and Oceans Canada (DFO) for the ten-day field operation.
"Catching these large, highly migratory turtles is challenging,” said Avens, who coordinated logistics for the project. “We are grateful for the opportunity to work with diverse collaborators to collect as much information from each capture as possible.”
The two-part field program involved satellite tagging and deploying a new suction-cup tag. Chris Sasso led the satellite tagging as part of the Atlantic Marine Assessment Program for Protected Species. Mike James (DFO) led the suction-cup tagging efforts. Seven leatherbacks received satellite tags, and the prototype suction-cup tag was tested for future use on leatherbacks off coastal New England.
Small Boats Key to Captures
“We tested out the idea of using small vessels for capturing and sampling leatherbacks and placing satellite tags on them in a pilot project during 2017 in Cape Cod Bay,” said Haas. “In Cape Cod Bay last fall, we also tested a new short-term, high-resolution tag developed by DFO and partners in Halifax, Nova Scotia. This year we put what we learned into practice and had a very successful tagging and sampling effort.”
Using two small boats outfitted with bow pulpits and observation platforms and a third small open-bow boat proved perfect for getting a leatherback turtle aboard between the two boats for examination, sampling, and tagging before releasing it back to the water. A spotter plane helped guide the boats to the turtles. Sasso's open-bow inflatable boat was custom-built to easily hold the netted leatherback and a few scientists. The turtles spent only about 20 minutes onboard before being released back to the ocean.
Once on the inflatable boat, researchers measured the leatherbacks, collected blood samples, and took ultrasounds to look at the fat layer and electrocardiograms (ECGs) to study heart activity, before attaching satellite tags to track their movements in the coming months.
Leatherbacks are the largest sea turtle, reaching lengths up to eight feet and weighing up to 2,200 pounds. The turtles were too large to weight on the small, open inflatable, but researchers did get length, width, and height measurements. The smallest turtle captured and sampled had a carapace of more than 4 feet long.
"All of the satellite tags are transmitting," Sasso said. Several turtles have remained on the continental shelf in coastal waters, while the others are out into deeper water offshore.
Testing Planned for Suction-Cup Tag
The second part of the field work involved testing a new suction-cup tag designed to monitor leatherbacks in fishing areas off the Northeast. Later this summer and fall, a team will be deploying the tags in Massachusetts waters. That project is part of the NOAA Fisheries Bycatch Reduction Engineering Program, and will be led by CFF with strong technical input from DFO, NEFSC, and nongovernmental organizations. During the field trials in North Carolina, the tags deployed well and collected depth information.
The new suction-cup tags are meant to stay on the turtles for several days. Each will have a video camera aimed at the turtle’s head, as well as sensors to record where it is and at what water depth. Researchers hope to see when and what the animal is eating and how they interact with their environment and with fishing gear. The tag can be tracked via radio signal. that way, it can be relocated and retrieved so the data it has collected can be downloaded. The information gathered may help researchers and fishery managers develop better strategies for mitigating the risk of capturing or injuring sea leatherbacks in fishing gear.