When diamondback terrapins spy bait sitting in a crab pot, they often push their way inside to feast, only to get stuck.
Terrapins, a small and vulnerable species, use lungs to breathe and can drown while trapped in cages underwater.
Conservation groups are asking Virginia regulators to require a solution: adding small gadgets to crab traps that keep terrapins out while still allowing crabs to enter.
“Virginia can take a really important step to saving this species by adopting this really simple, cheap, easy rule,” said Will Harlan, Southeast director and senior scientist with the Center for Biological Diversity.
The organization, along with the Virginia Herpetological Society and nonprofit Wild Virginia, petitioned the Virginia Marine Resources Commission earlier this year to require what are called turtle excluder devices on any crab pots used less than 150 yards from shore.
The commission will consider the petition on June 24.
Diamondback terrapins are the only turtle in the U.S. to live in brackish water, which is a mix of freshwater and saltwater that makes up most of the Chesapeake Bay.
The terrapin is considered a keystone species because of its role as a predator that helps maintain the salt marsh ecosystem and ingestion of eelgrass seeds, which helps distribute the seeds throughout the environment, according to the Virginia Department of Wildlife Resources.
The turtles were heavily harvested in the late 19th and early 20th centuries and now face pressure from development and other human activities on their habitat and nesting areas, Virginia officials say.
Harlan said the population of terrapins along the Atlantic and Gulf coasts has plummeted by about 75% in the last 50 years. The federal government is in the process of studying whether to list the species as endangered.
“They’re in trouble,” Harlan said. “And the biggest threat to terrapins are crab traps.”
Roughly 60,000 to 80,000 terrapins drown in crab pots each year, he said.
Turtle excluder devices, or TEDs — also known as bycatch reduction devices — have been around for decades.
Biology professor Randy Chambers has studied the issue since he started working at William & Mary in 2001.
The devices work just as they sound, he said, narrowing the openings that allow marine life into crab traps.
“The shells of a turtle are much higher in profile than the shell of a crab, so crabs can still slip into the traps,” Chambers said. “But turtles are excluded.”
He and other researchers at William & Mary’s Keck Lab have spent years studying the effectiveness of various designs of TEDs, combining different shapes, colors and materials.
“The overall impact of all these different bycatch reduction devices has been a dramatic reduction in the bycatch of terrapins” – a decrease of about 90%, Chambers said.
The Keck Lab uses 3D printers to produce a red, oval-shaped device designed by a research associate. Crabbers can also simply narrow the funnels of their cages using standard wire when constructing traps, he said.
Maryland officials recognized back in the 1940s that the design of crab traps also attracts animals such as turtles, diving birds and muskrats, Chambers said. The state banned the use of commercial-style traps in tributaries of the Chesapeake Bay. In 2000, Maryland started requiring the use of TEDs.
The VMRC currently “strongly encourages” TEDS for all recreational crab pots, and offers discounted fees for those who do so.
Harlan said the lack of regulation puts Virginia behind other East Coast states.
“Virginia's kind of the last holdout, and is probably the most important habitat for diamondback terrapins,” he said.
Many commercial crabbers in Virginia oppose the proposed regulation.
“Without concrete research, implementing TEDs in crab pots could be an unnecessary burden on the crabbing industry rather than a proven conservation measure,” watermen wrote in a public comment to VMRC.
“More studies would be required to determine if there is any legitimate risk to turtle populations before requiring additional modifications to crab pots in Virginia waters.”
Chambers said research shows a slight reduction in crab catch when TEDs are used – a significant effect in an industry already facing challenges with a declining crab population.
The devices cost only about $1 or $2, but having to buy hundreds of them would be another economic constraint.
However, environmental groups’ petition to VMRC requests regulation only for waters within 150 yards of shore, where most crabbing is recreational.
Harlan said they’re open to any measures the commission would be willing to enact, such as limiting the rule to recreational crabbing.
“This species is really important socially and culturally for the entire region and especially Virginians. This is their turtle,” he said. “Keeping terrapins around means keeping our marshes healthier.”
