Quantifying Sea-Turtle Impacts on Turtle-Excluder-Devices in Shrimp Trawls in the Gulf of Mexico

Several species of sea turtles native to the Gulf of Mexico and the Atlantic Ocean are listed as endangered under the Endangered Species Act. The capture of sea turtles as bycatch during shrimp trawling has been cited as a significant contributor to sea turtle population declines. The impact of shrimp trawling on sea turtle populations has been difficult to ascertain, primarily because it is difficult to estimate turtle relative abundance and turtle bycatch with any degree of accuracy. Turtle Excluder Devices (TEDs) have been required by law in the Gulf of Mexico shrimping industry since the late 1980’s to reduce the number of bycaptured turtles taken during shrimp trawling activities. Personnel with the National Oceanic and Atmospheric Administration (NOAA) are responsible for continued verification of the efficiency of the TEDs. To do this, they developed an underwater camera system to monitor wild-caught turtles in the Gulf of Mexico and observe their escape times. The goal of the current project is to record sound underwater these verification operations and use the sound of turtles impacting the TEDs to quantify the number of turtles encountered. In conjunction with NOAA personnel, a 10-day excursion on a shrimp trawling vessel was made in May 2022. A camera and a hydrophone were deployed inside two trawling nets close to the TED to record the audio and video during trawling operations. Researchers aboard the vessel monitored the video feed on screens to record the time of impact and species for turtle encounters in each of the two nets deployed. During the ten day trip, the researchers on the vessel observed 51 turtles that went through the nets, impacted the TEDs, and escaped. In addition, several rays and sharks also went through. Analysis of this acoustic data and preliminary results will be presented.