PS 22-96 - Man-made rock jetty on the Louisiana coast serves as developmental habitat for juvenile green turtles, Chelonia mydas

Wednesday, August 10, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
Devon A. Nemire-Pepe1, Mandy C. Tumlin2, Andrew G. Crowder1 and Kristen M. Hart3, (1)U.S. Geological Survey, Davie, FL, (2)Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA, (3)Wetland and Aquatic Research Center, U.S. Geological Survey, Davie, FL

Five species of marine turtles, all federally listed as threatened or endangered, reside in the Gulf of Mexico. Many anthropogenic factors such as dredging, trawling, hook and line capture, debris ingestion and entanglement, and boat propeller collisions threaten turtle survival. These threats were then compounded by the Deepwater Horizon oil rig explosion on April 20, 2010.  This massive spill, approximately 66 km off the Louisiana coast, released millions of barrels of oil into the Gulf of Mexico, fouled and killed marine turtles, and heavily impacted critical habitat for all five species of marine turtles. Long term assessments are necessary to evaluate the impacts of the spill on marine turtle populations, especially in the northern Gulf. Stranding data indicates that coastal bays in the Gulf are important habitat for juvenile marine turtles, but there are still gaps in our knowledge of juvenile habitat utilization patterns. Here we begin laying the foundation for a mark-recapture study of juvenile and sub-adult marine turtles at Belle Pass, a heavily trafficked channel that leads into Port Fourchon on the Louisiana coast. We captured turtles along a 0.64 km stretch of rock jetty using dip nets in December 2014, May 2015, and December 2015.


We captured 69 turtles, with 64 first-time captures and 5 recaptures. Juvenile green turtles, Chelonia mydas, constituted 98.4% of the captures. Green turtle curved carapace length (CCL) ranged from 26.0 to 45.7 cm with a mean of 33.2 ± 4.4 cm. The only other sea turtle species captured was a sub-adult loggerhead (Caretta caretta; CCL= 77.5 cm). The high concentrations of turtles found at this jetty is similar to aggregations noted for other sea turtle studies conducted in Texas, which reported that jetty habitat received a disproportionately high amount of use. Due to the large concentrations of juvenile green turtles found in such a small area this jetty habitat may represent a critical developmental habitat for green turtles. In addition to collecting morphometric data, we also collected blood and biopsy punches for future genetic and isotope studies. This information will help to give us a better idea of where these juveniles are recruiting from and what their diet consists of. Likely drawn by the abundance of algae on the rocks, this man-made jetty serves as year-round habitat for these turtles.