Because marine turtles come ashore to nest, the adult (female) life-stage is most widely studied. However, much less information is available about habitat use and movements of sub-adults and juveniles; both Recovery Plans for the Kemp’s ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) turtles include monitoring population abundance, trends and demographic parameters of these life-stages. Only recently has information become available about marine turtle high-use areas along the northern Gulf of Mexico (GoM) coast. 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. In May 2016 we initiated a study that directly addresses those recovery and protection goals and provides information on in-water aggregations of immature and adult marine turtles of both sexes in the northern GoM. USGS, with support from the Bureau of Ocean Energy Management, is utilizing trawling operations to opportunistically tag sea turtles with depth-logging satellite tags and collect biological samples to inform specific management decisions related to trawling and dredge operations.
Results/Conclusions
Turtle tracks (N=26) are providing data needed to validate the distance required for relocation which could help examine the economic feasibility of contracted dredge projects and prevent multiple handlings of the same turtle. To date, 16 loggerheads (mean straight carapace length (SCL) 83.2 cm) ranging in size from 72.7-97.2 cm SCL (SD 7.6) and 10 Kemp’s ridleys (mean SCL 62.3 cm) ranging in size from 56.6-67.5 cm SCL (SD 3.4) have been tracked from two in-water capture sites, one off the southern Louisiana coast and one off Pensacola, Florida, for > 2000 days. Turtles include sub-adults, males, and females of both species. All turtles showed fidelity to capture sites, with displacement of 6-47 km for Kemp’s ridleys and 1-63 km for loggerheads. Depth-use data so far indicates that loggerheads are diving slightly deeper and longer than Kemp’s ridleys; >30% of all loggerhead dives were 20-25 m and >50% of all Kemp’s ridleys dives were 10-15 m, and >44% of all loggerhead dives were 15-30 minutes whereas >40% of all Kemp’s ridley dives were 0-15 minutes. The study is generating key information on sea turtle use of discrete foraging areas, general sea turtle distribution patterns across space and time and sea turtle dive profiles and patterns.