Discerning behavioral patterns of sea turtles in the Gulf of Mexico to inform management decisions
The USGS (US Geological Survey) is partnering with BOEM (Bureau of Ocean Energy Management) to sample and tag sea turtles captured during relocation trawling efforts performed in conjunction with dredging operations. This project will provide data to inform management decisions related to oil and gas activities in the Gulf of Mexico (GOM). In particular, we will provide new data to be used in decisions related to dredging operations at sites with high likelihood of turtle presence.
for the full map
- Partner with relocation trawling operations that use hopper dredges to opportunistically tag sea turtles and collect biological samples for later analysis.
- Use tracking information to provide data needed to validate the distance needed for relocation, which could help the economic feasibility and prevent multiple handlings of the same turtle.
- Apply this information to inform other program areas such as decommissioning of oil rigs (by evaluating dive times) and optimization of current sea turtle visual and aerial survey efforts using data gathered on time spent in the upper two meters of the water column.
Determining distribution, seasonal movements, vital rates and habitat use for all life-stages of marine turtles has been identified by the U.S. Fish and Wildlife Service (USFWS) and the U.S. National Marine Fisheries Service (NMFS) as a major action required to achieve recovery for these endangered species (NMFS and USFWS 1991). The green turtle recovery plan (NMFS and USFWS 1991) also states that “to adequately protect and enhance survival of sea turtles, we must know where they occur, in what numbers, at what times, and what factors contribute to mortality.” Because turtles come ashore to nest, the adult (specifically, female) life-stage is most easily studied; however, much less information is available about habitat use and movements of sub-adults and juveniles. Only recently has information become available about sea turtle high-use areas along the GOM coast (Hart et al. 2013, Shaver et al. 2013, Foley et al. 2014, Hart et al. 2014). However, fine-scale information on dive profiles is still lacking for sea turtles in the GOM. Such information can provide key data on time spent per individual in various portions of the water column, in specific locations. This study will directly address those recovery and protection goals and provide information on in-water aggregations of sub-adult, juvenile, and adult marine turtles in the GOM.
The following field methods are proposed utilizing turtle capture through relocation trawling activities during dredging projects off the Louisiana coast:
- Flipper, Passive integrated transponders (PIT), and satellite telemetry tags will be deployed on all life stages of individuals to track turtles at foraging grounds to determine site-fidelity, depth use, drivers of local movements and track movements of turtles away from and within sampling/capture sites in the dredged borrow area;
- Accelerometer data loggers (ADLs) deployed using a VHF transmitter and galvanic timer release;
- Biological sampling using skin and carapace biopsies and bilateral cervical sinus blood sampling;
- Gastric lavage to sample gut content for diet, isotopes, and collection of opportunistic by-catch species; and
- Sample all turtles for genetics to determine stock of origin and population connectivity.
- Castelblanco-Martínez, D.N., Padilla-Saldívar, J., Hernández-Arana, H.A., Slone, D.H., Reid, J.P., and Morales-Vela, B., 2012, Movement patterns of Antillean Manatees in Chetumal Bay (Mexico) and Coastal Belize: a challenge for regional conservation: Marine Mammal Science, n/a–n/a. doi:10.1111/j.1748-7692.2012.00602.x.
- Foley, A.M., Schroeder, B.A., Hardy, R., MacPherson, S.L., and Nichols, M., 2014, Long term behavior at foraging sites of adult female loggerhead sea turtles (Caretta caretta) from three Florida rookeries: Marine Biology, 161(16), 1251-1262, doi:10.1007/s00227-014-2415-9.
- Hart, K.M., Lamont, M.M., Sartain, A.R., Fujisaki, I., and Stephens, B.S., 2013, Movements and habitat-use of loggerhead sea turtles in the northern Gulf of Mexico during the reproductive period: PLoS ONE 8(7), e66921, doi:10.1371/journal.pone.0066921.
- Hart, K.M., Lamont, M.L., Sartain, A.R., and Fujisaki, I., 2014, Residency and foraging patterns of Northern Gulf loggerheads: implications of local threats and international movements: PLoS ONE 9(7), e103453. doi:10.1371/journal.pone.0103453.
- National Marine Fisheries Service and U.S. Fish and Wildlife Service, 1991, Recovery plan for U.S. population of Atlantic Green Turtle: National Marine Fisheries Service, Washington, DC.
- National Marine Fisheries Service and U.S. Fish and Wildlife Service, 2008, Recovery plan for the Northwest Atlantic population of loggerhead sea turtle (Caretta caretta), second revision: National Marine Fisheries Service, Silver Spring, MD.
- National Marine Fisheries Service, U.S. Fish and Wildlife Service and SEMARNAT, 201, Bi-national recovery plan for the Kemp’s ridley sea turtle (Lepidochelys kempii), 2nd revision: National Marine Fisheries Service. Silver Spring, MD.
- Shaver, D.J., Hart, K.M., Fujisaki, I., Rubio, C., Sartain, A.R., Peña, J., Burchfield, P.M., Gomez Gamez, D., and Ortiz, J., 2013, Foraging area fidelity for Kemp’s ridleys in the Gulf of Mexico: Ecology and Evolution, 3(7), 2002-2012, doi: 10.1002/ece3.594.