Abstract
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. However, 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 southeastern United States shrimp trawl industry beginning in the late 1980’s in order to reduce the number of bycaptured turtles taken during shrimp trawling activities. These devices typically consist of a large metal grate that allows the passage of shrimp and small fish into the bag of the trawl, but forces larger animals (particularly turtles) out through a flap either on the top or bottom. Acoustic measurements may provide a method of estimating turtle bycatch by detecting the sound made by turtles impacting the metal TED. As part of his work testing the efficiency of TEDs, Daniel Foster (NOAA) collected visual and acoustic data using a hydrophone and a camera attached to a TED. This acoustic data was analyzed by The University of Mississippi National Center for Physical Acoustics (NCPA) personnel using low-pass filters and band-power calculations. This proof of concept analysis indicated that turtle impacts have acoustic signatures that are distinguishable from other wildlife encountered in the trawl. Larger and more diverse datasets are needed to validate these trends and develop an algorithm to identify turtle impacts on TEDs. Results from this proof of concept data set and analysis will be presented.
