Sea Turtle Bycatch Mitigation in the Southeastern US Skimmer Trawl Fishery: Size Matters

Between May and July 2012, observers reported 24 Kemp’s ridley (Lepidochelys kempii) sea turtles captured aboard southeast U.S. skimmer trawl vessels targeting penaeid shrimp.   The size distribution of turtles captured was small with 58% having body depths (BD) less than 4-inches (10.2 cm), which could allow them to pass through maximum 4-inch Turtle Excluder Device (TED) bar spacing proposed for the fishery.  Examination of in-water and stranding data indicated that reducing TED bar spacing to 3-inches (7.6 cm) would prevent > 97% of sea turtles from passing through deflector bars.  In June 2014, researchers addressed this issue through a sea turtle exclusion study with reduced bar spacing TEDs.  Captive-reared, one year-old loggerhead (Caretta caretta) and Kemp's ridley sea turtles were exposed to a variety of TED treatment configurations to examine escape rates.  Logistic regression analysis identified species (p<0.0001), TED type (p<0.0163), and flap twine size (p<0.0001) as significant predictors of turtle capture.  The same TED configurations examined for turtle exclusion were evaluated for target shrimp retention in 2013 and 2014.  Results indicate increased catch loss with finer twine (1.8 mm) TED flaps when compared to traditional (2.3 mm) flaps.