Every summer the crew of the R/V Georgia Bulldog works with the South Carolina Department of Natural Resources to study regional sea turtle abundance.
The capture of live animals with in-water surveys offers a picture of relative abundance over a specific time period and the chance to study population structure.
In-water surveys use bottom trawling (a strong fishing net drug along the sea bottom) to capture sea turtles in coastal waters. In South Carolina DNR's in-water sea turtle research, sea turtles are caught, biological samples taken and measurements, observations and associated bycatch recorded. The University of Georgia's Marine Extension Service (MAREX) is a primary project partner with the R/V Georgia Bulldog and crew providing both vessel and manpower.
Cape Canaveral Sea Turtle Research
During 2006 and 2007, the South Carolina Department of Natural Resources (SCDNR) and the University of Georgia's Marine Extension Service (MAREX) partnered to study the reproductive biology and seasonal distribution patterns of adult male loggerhead sea turtles.
Using modified shrimp trawl nets known as "turtle nets" (no turtle excluder device and larger mesh to minimize by-catch), short-duration drags were conduced aboard the R/V Georgia Bulldog in the shipping entrance of Port Canaveral, Florida.
Sampling was completed in April in both years, the time of year with the greatest probability of collecting adult male loggerhead sea turtles in this shipping entrance channel.
This recent work was novel in several respects. First, most of the adult male loggerheads collected in this study were satellite-tagged to document their local distribution patterns during the mating season, as well as to determine the locations and water depths where this very elusive component of loggerhead populations along the U.S. East Coast spend the remainder of the year.
During the study, researchers collaborated to gain as much information as possible from the loggerheads before they were released. Vet students were able to learn how to perform scute scraping, while members of the research crew performed biopsies and blood samples to collect samples to analyze for contaminants. Among other analyses, blood tests conducted aboard the vessel confirmed which animals were healthy enough to participate in the study.
In addition to laparoscopic examination to characterize reproductive activity of individual male turtles prior to attachment of satellite-transmitters, an additional non-invasive reproductive technique was utilized: ultrasound.
Although ultrasound cannot provide some data that is possible with invasive laparoscopy, by comparing ultrasound and laparoscopic images for a large sample size of adult male loggerheads, researchers hope to be able to validate this non-invasive technique for characterizing many reproductive aspects of sea turtles in the future.
In total, 38 individual adult male loggerheads were collected and sampled during the 15 sea days of this study, of which 29 were satellite tagged. Reproductive data for nearly all adult male loggerheads collected indicated that they were actively mating with adult female loggerheads in the vicinity. However, satellite-telemetry data revealed that some of these reproductively-active turtles were migratory, while others were long-term residents.
The migratory group remained close to shore during April and May before quickly emigrating away from Canaveral by the end of May, while the resident group shifted to the deep waters of the continental shelf offshore of Canaveral at about the same time that migratory animals also left the area.
Migratory animals dispersed along the U.S. East Coast and into the Gulf of Mexico to a number of different areas ranging from New Jersey to the Florida Keys and the Florida Panhandle, encompassing nearly entire extent of nesting range for loggerhead sea turtles in North America.