Debilitated Loggerhead Turtle (Caretta caretta) Syndrome Along the Southeastern U.S. Coast: Incidence, Pathogenesis, and Monitoring
American Association of Zoo Veterinarians Conference 2004
Terry M. Norton1, DVM, DACZM; Mark Dodd2, MS; Al Segars3, DVM; Jennifer M. Keller4, PhD; Margie Peden-Adams5, PhD; Rusty D. Day4, MS; Craig Harms6, DVM, PhD, DACZM; Elliott Jacobson7, DVM, PhD, DACZM; Allen M. Foley8, PhD; Sally Murphy9, MS; Wendy Cluse10, BS; Wendy Teas11, BS; Michael Bresette12, BS; Barbara Schroeder13, BS; Adam Mackinnon2, BS; Nancy Stedman14, DVM, PhD, DACVP
1St. Catherines Island Wildlife Survival Center, Wildlife Conservation Society, Midway, GA, USA; 2Nongame Wildlife and Natural Heritage Section, Georgia Department of Natural Resources, Brunswick, GA, USA; 3Marine Division, South Carolina Department of Natural Resources, Beaufort, SC, USA; 4Hollings Marine Laboratory, National Institute of Standards and Technology, Charleston, SC, USA; 5Marine Biomedicine and Environmental Science Center (MBES), Medical University of South Carolina (MUSC), Charleston, SC, USA; 6Center for Marine Science and Technology, North Carolina State University, Moorehead City, NC, USA; 7Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA; 8Florida Marine Research Institute, Florida Fish and Wildlife Conservation Commission, Jacksonville, FL, USA; 9South Carolina Department of Natural Resources, Charleston, SC, USA; 10North Carolina Wildlife Resources Commission, Atlantic Beach, NC, USA; 11National Marine Fisheries Service, Miami, FL, USA; 12Quantum Resources, St. Lucie Power Plant, Jensen Beach, FL, USA; 13Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA; 14Athens Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
Abstract
In 2003, there was a perceived increased occurrence of emaciated and barnacle-laden loggerhead turtles (Caretta caretta) found stranded (both dead and moribund) along the southeastern U.S. Atlantic coast. To investigate this situation further, the Wildlife Conservation Society’s St. Catherines Island (SCI) Wildlife Survival Center (WSC) and the Georgia Department of Natural Resources organized a workshop on SCI in November of 2003. Fifteen people attended including turtle biologists from Florida, Georgia, South Carolina, and North Carolina; veterinarians; toxicologists; immunologists; and representatives from the National Oceanic and Atmospheric Administration (NOAA).
The group determined that there was an increasing trend in strandings of debilitated sea turtles from 1992–2002 (approximately 11% annual increase). The number of debilitated turtles appeared to increase substantially in 2003 (NC 3%, SC 22%, GA 10%, and FL 20.2% of the total turtle strandings). The species composition of debilitated sea turtle strandings was primarily loggerheads, but a few green (Chelonia mydas), Kemp’s ridley (Lepidochelys kempii) and possibly, in Florida, a hawksbill (Eretmochelys imbricata) turtles were affected. Temporally, the stranding of debilitated turtles occurred all year in Florida; however, strandings were found to be concentrated in the spring and summer (April through July) in the other states. Spatially, debilitated sea turtles were stranded across the southeastern U.S. coastal region, there were areas of high stranding density in the southern part of North Carolina, the northern part of South Carolina (Georgetown and Horry Counties) and around Cape Canaveral in Florida (Brevard County). Many explanations for stranding patterns were discussed including ocean currents, winds, and cold-stunning events.
A debilitated turtle was defined as emaciated with small barnacles covering the skin. The flippers can also have lesions or be necrotic. While heavy epibiota can be a normal finding on the carapace and plastron of healthy loggerhead sea turtles, the skin is generally free of these commensals. Health assessment and necropsy data from these cases indicated the turtles were being affected by a wide range of secondary bacterial and parasitic infections with the primary cause still to be determined. Seven debilitated turtles showed significantly higher blood levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides compared to apparently healthy turtles (Keller, et al., unpublished data). In a separate study, mercury concentrations in blood and scutes were 2 to 3 times higher in dead stranded turtles compared to live, apparently healthy turtles although the sample size was small (R. Day, unpublished data). It is still unclear at what levels these compounds become toxic to sea turtles. The high contaminant levels could be a secondary effect as debilitated turtles use up their fat reserves, causing organic contaminants to become concentrated in blood.
The group determined several areas that need to be addressed in 2004. First, a complete statistical analysis of debilitated sea turtle stranding trends (NMFS-Sea Turtle Stranding and Salvage Network Database) is needed to better define the extent of the problem. This analysis will assist in determining if there was a substantial and statistically significant increase of stranded debilitated turtles in 2003. Possibly the strandings correlate with overall increases in offshore populations. Ongoing studies at the St. Lucie Power Plant in Florida indicate a significant increase in loggerhead sea turtle populations. The average annual captures of this species from 1992–2002 was 275, while in 2003, 538 turtles were captured. Stranding reporting protocols will be reviewed to ensure that debilitated turtle strandings can be accurately assessed. In the past, not all strandings were examined for signs of debilitation. Thus, the percentage of debilitated turtles should be expressed as a proportion of turtles examined, not total strandings.
In order to provide consistent, standardized documentation on debilitated turtles that strand in 2004, protocols are being developed to include visual assessment, physical examination, morphometrics, clinical pathology, contaminant analysis, immune function tests, gross necropsy and histopathology.
Acknowledgments
We would like to thank the St. Catherines Island Foundation and the WSC for hosting the meeting on St. Catherines Island.