Shrimp fishermen pull trawl nets through the water behind their boats, catching tens of millions of pounds of valuable shrimp each year. Sea turtles can also get captured in these trawls and drown. Sea turtles need to surface to breathe. This accidental catch is an example of bycatch and is a major threat to sea turtle populations.
In the early 1980s, shrimp fishermen and NOAA scientists worked together to develop a solution: turtle excluder devices. A TED is a metal grid placed in the end of a trawl net. If a turtle gets caught in the net, the TED directs it out through an escape opening.
TED implementation in the Southeast U.S. shrimp fishery is considered one of the greatest sea turtle conservation accomplishments in recent history. This gear innovation is 97 percent effective at excluding turtles when properly installed and maintained in trawl nets. TEDs also benefit America’s shrimp fleets by clearing debris from the catch, reducing bycatch of other species like stingrays and sharks, and increasing the quality of shrimp catches.
A Collaborative Approach to Designing and Using TEDs
Together with fishermen, gear specialists at the Southeast Fisheries Science Center work to reduce sea turtle bycatch by developing and testing commercial fishing gear modifications like TEDs. They also help fishermen by providing courtesy TED compliance inspections and training on the proper use and installation of TEDs. This critical work is currently funded through the Deepwater Horizon Sea Turtle Early Restoration Project, managed by the Regionwide Trustee Implementation Group.
“Having worked as commercial fishermen prior to entering government service, many of our staff bring a unique credibility to their collaborations with industry, which strengthens relationships and builds trust between fishermen and the agency.” —Jeff Gearhart, Harvesting Systems Branch Chief, Southeast Fisheries Science Center
While TEDs have been in use since the 1980s, NOAA gear specialists and fishermen continually modify and improve them. NOAA originally approved five TED designs in 1987. The designs have evolved to include a variety of grid shapes, straight or bent bars, top or bottom openings, and single, double cover, or flapless openings. All approved TED designs must be able to complete two key tasks: exclude and protect turtles and retain target shrimp catch. To ensure high adoption and compliance rates of new TED designs following any rulemaking, NOAA leads extensive outreach, including workshops, training sessions, and industry-wide Fishery Bulletin announcements.
Shrimpers and the fishing industry can propose changes to improve performance of TEDs to NOAA gear specialists. We work with them to refine their suggestions, test modifications, and certify those that meet the requirements. This collaborative approach towards TED modifications allows fishermen to propose methods of preserving their catch while still protecting sea turtles.
This process led to the approval of the Chauvin flapless TED. It includes a 3-inch PVC pipe installed along the leading edge of the escape opening to improve shrimp retention and minimize bycatch of other incidentally captured marine species. Initially, a fisherman brought the design to our gear specialist team with a broom handle installed along the leading edge of the opening. After testing, the team found that the broom handle did not flex enough for large turtles to escape easily. They swapped the broom handle for an equal size PVC pipe to resolve this issue. A variation of this TED modification is the Drury flapless TED, which is currently under trial.
We recently completed a restoration project funded by the Deepwater Horizon Open Ocean Trustee Implementation Group to reduce juvenile sea turtle bycatch in the shrimp otter trawl fishery. This project is another example of innovation and collaboration between NOAA and commercial fishermen. The project team worked with industry to develop and test TEDs with narrower spacing between the bars to determine if small juvenile sea turtles could more easily escape. The new TED designs successfully excluded small turtles and maintained shrimp retention rates. The Open Ocean Trustee Implementation Group will now make these tested TED configurations available for shrimpers who would like to voluntarily use them.
Benefits to Fishermen
TEDs decrease bycatch of other marine species like sharks and stingrays. This improves safety for fishermen working on deck and prevents additional accidental catch of non-target species. The devices also reduce the amount of marine debris caught in trawls. Trawls encounter a wide variety of debris, including manufactured objects like tires and crab pots. Debris can crush shrimp and damage the net. TEDs stop debris from passing through the trawl and direct it out through the escape opening, leading to better quality product, while reducing gear repair expenses.
Trawl nets with TEDs may also outfish those without TEDs, because the device prevents the mouth of the net from narrowing. A simple way to picture this effect is to imagine the trawl net as a sock. Pulling back harder on the end of the sock will narrow the opening. The same is true for trawl nets. If the nets capture large debris or species like turtles and sharks, they create more drag, causing the opening of the net to narrow. By allowing debris and turtles to exit the net, the TED can reduce drag, allowing the net to maintain its spread and catch more shrimp.
Sea Turtle Conservation and Recovery
All sea turtle species are protected under the Endangered Species Act. Five of the six sea turtle species found in U.S. waters also occur within the Gulf of America where 70 percent of domestic shrimping occurs. Sea turtles are vulnerable to shrimp trawls because they migrate, rest, and forage in the areas where shrimpers fish. Two species, loggerhead and Kemp’s ridley sea turtles, are particularly affected by bycatch because their foraging habitats overlap with shrimping grounds.
Today, there is evidence that worldwide most sea turtle populations are rebounding. The use of TEDs in U.S. trawl fisheries in the Gulf of America and nest protection efforts in Mexico are key factors contributing to the increase in Kemp’s ridley sea turtles. In 1996, the main nesting beaches for Kemp’s ridley turtles in Mexico saw around 2,000 nests. By 2022, this number had increased to around 17,000 nests. The widespread use and improvement of TEDs can reduce the threat of bycatch and help sea turtle populations recover.
