Assessing and tracking resident, immature loggerheads (Caretta caretta) in and around the Flower Garden Banks, northwest Gulf of Mexico

Abstract

Over five years of underwater/above water surveys resulted in 140 reports documenting 153 sea turtle sightings within the boundaries of the Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico. It has been determined that a population of large immature loggerheads resides at and moves in close proximity to the East and West Banks of the FGBNMS. Stetson Bank, the smallest bank under the Sanctuary's jurisdiction, is a sponge and Millepora habitat. We have determined that this bank is a more likely habitat for hawksbill sea turtles. Six large immature loggerhead sea turtles (Caretta caretta) with carapace lengths (CCL) ranging from 70.5-101 cm were captured at depth by SCUBA divers. Five of the six were outfitted with radio and/or satellite transmitters. Five of the six animals were females. A pubescent male was recaptured three times over a period of 20 months. Over 40% of the satellite locations fell within the Sanctuary boundaries. Geographic Information System (GIS) analysis revealed an average core range of 133.6 km² and an average home range of 1074 km². These ranges are not significantly different from satellite tagged C. caretta captured underneath oil and gas platforms in the Gulf of Mexico. The average core ranges fell within one kilometer of the Sanctuary boundaries, and the home range within 30 km of the Sanctuary boundaries. Recommendations are made to the National Oceanic and Atmospheric Administration's (NOAA's) Marine Sanctuary Division for the use of core and home range analyses and satellite fix proximity relationship to assist with management decisions.