Evaluations of turtle excluder devices (TEDs) with reduced bar spacing in the inshore penaid shrimp fishery of the northern Gulf of Mexico

Abstract

Turtle Excluder Devices (TEDs) have been required in the southeastern United States penaeid shrimp trawl fishery since 1989 to reduce the mortality of sea turtles associated with shrimp trawling. TEDs are metal sorting grids placed in the trawl forward of the codend. Larger animals, such as sea turtles, are directed to an escape opening in the trawl, while smaller ones, including shrimp, pass through the grid bars and into the codend. Federal TED requirements set the maximum bar spacing for the TED grid at 4 inches (10.2 cm) due to the size range of sea turtles that were encountered when the regulation was enacted. To explore the additional bycatch reduction benefit that may be achieved by reducing the maximum TED bar spacing, the NOAA Southeast Fisheries Science Center (SEFSC) conducted a series of experiments to evaluate TEDs with bar spacing of 2-inches (5.1 cm). Two prototype TED designs, a 2-inch and a 2-inch staggered bar (SB) TED, were compared to identical TED designs with 4-inch bar spacing (controls) during paired trials conducted in the inshore shrimp fishery of the northern Gulf of Mexico. The results of the study show that the 2-inch and the 2-inch SB TED, reduce the targeted shrimp catch by a statistically significant amount, 8.8% and 4.5% respectively. Both experimental TED designs reduced the bycatch of croaker (Micropogonias undulates), the most abundant bycatch species. However, only the 2-inch TED showed a significant reduction (30.7%, p <0.001). The reduction rate of sharks with the 2-inch and 2-inch SB TED was 83.9% and 55.2% respectively, with significance being detected for the 2--inch TED. The observed reduction in rays was statistically significant for both experimental TED designs with a mean reduction of 82.5% and 65% for the 2-inch and 2-inch SB TED, respectively.