A Turtle Excluder Device (TED) is a specialized grid system integrated into a trawl net. Its primary function is to enable marine animals, particularly sea turtles, to escape after being captured, while allowing the intended catch, such as shrimp, to be retained.
TEDs are constructed from materials like metal bars and mesh, placed within the trawl’s funnel-shaped body. This design facilitates the separation of larger bycatch from target species, promoting conservation without significantly impacting fishing operations.
NOAA Fisheries indicates that when properly deployed, modern TED designs can be up to 97 percent effective in excluding turtles from shrimp trawls. This technological solution addresses a significant environmental concern by allowing turtles to exit the net unharmed.
The Threat of Trawling to Sea Turtles
Trawl nets, especially those used in shrimp fishing, pose a considerable threat to sea turtles due to their indiscriminate nature. These large, cone-shaped nets are dragged along the ocean floor, capturing virtually all marine life, including non-target species. This incidental capture is known as bycatch.
Sea turtles are air-breathing reptiles, making them vulnerable to drowning when trapped underwater for extended periods in fishing nets. Many U.S. sea turtle species, such as loggerheads, green turtles, and leatherbacks, are listed as threatened or endangered under the Endangered Species Act.
Bycatch from shrimp trawling has historically been a significant contributor to sea turtle mortality, with thousands of turtles impacted annually by U.S. fisheries alone. Worldwide, bycatch is estimated to cause hundreds of thousands of sea turtle deaths each year, underscoring this global conservation issue. The development of exclusion devices became a priority to mitigate this widespread impact on vulnerable sea turtle populations.
Mechanical Function of a TED
A standard Turtle Excluder Device consists of a rigid or semi-rigid grid, often made of metal bars, installed at an angle inside the trawl net. This grid acts as a physical barrier, intercepting larger marine animals. Beyond this grid, an escape opening, usually a flap or a hole, is incorporated into the net’s mesh.
The optimal grid angle for these devices typically ranges between 40 to 60 degrees from the horizontal flow of water. When a trawl net is deployed, shrimp and other smaller organisms pass through the evenly spaced bars of the grid and are collected in the codend, the back portion of the net.
Larger animals like sea turtles, sharks, and rays are blocked by the grid due to their size. The angled design of the grid then guides these animals towards the strategically placed escape opening.
Different TED designs exist, such as top-opening or bottom-opening, which cater to varying turtle behaviors and specific fishing conditions. For example, the NAFTED, a common model, features a top-opening door. This mechanism allows turtles to be ejected from the net without having to swim back through the net’s mouth, leveraging the water flow to direct them out.
Implementation and Regulations
The use of Turtle Excluder Devices is primarily mandated for shrimp trawlers in U.S. coastal waters, including the Atlantic and the Gulf of Mexico. These regulations, in effect since 1987, were established under federal law to comply with conservation statutes such as the Endangered Species Act. Federal regulations (Title 50, Section 223 of the U.S. Code of Federal Regulations) detail requirements for TED usage and sea turtle protections.
Beyond domestic waters, similar requirements influence international trade. Section 609 of U.S. Public Law 101-162, enacted in 1989, stipulates that shrimp harvested by foreign fleets cannot be imported into the United States unless the exporting nation is certified as having a sea turtle protection program comparable to that of the U.S. This often involves the mandatory use of TEDs or demonstrating that their fishing methods do not pose a threat to sea turtles.
The U.S. Department of State, with technical advice from NOAA Fisheries, conducts annual certifications to ensure compliance, promoting the international adoption of TEDs. Countries like Australia, Brazil, and France have established systems to monitor TED use for shrimp exports to the U.S. market. This policy encourages global efforts to reduce sea turtle bycatch and supports sustainable fishing practices worldwide.