Abstract

Stingray City is a well-known tourist attraction in Grand Cayman where southern stingrays (Dasyatis americana) are known to congregate and visitors can feed and interact with the animals. Boat operators provide food items to tourists for them to feed to the rays to facilitate close interaction. Predominately squid and other non-natural food items are utilized. Population assessments in early 2012 showed a decline in stingray numbers at the Sandbar site with stakeholders expressing concern that human interaction may be contributing to the decline in the population of rays. Some of the hypotheses for the cause of the population decline include: poor nutrition, disease (viral, fungal, bacterial, parasites) due to possible overcrowding, predation by sharks, and poaching or collecting by humans. The goal of this study was to measure indices of health, stress, and nutritional status from southern stingrays in Grand Cayman to identify potential analytes for population decline. Over a four day period, 71 southern stingrays were handled for blood collection, morphometrics and tissue biopsies. If an animal had not been previously implanted with a PIT tag, that was done at the time of handling. Rays were caught by snorkelers or SCUBA divers at 3 different locations with the bulk of the animals coming from the Stingray City Sandbar tourist site. Blood samples were analyzed for over 90 indices including blood gas parameters, complete blood counts, comprehensive chemistries, trace minerals, heavy metals, vitamins, fatty acid profiles, sex and stress hormone levels and serum protein fractions via electrophoresis. Preliminary results suggest that for the majority of the analytes measured, no differences were detected between the three sample locations and values were comparable to those measured in both captive and other free-ranging southern stingray populations.¹ Significant differences were detected in the major essential fatty acids (C20:4n6 arachidonic acid, C22:6n3 docosahexaenoic acid, and C20:5n3 eicosapentaenoic acid) between locations, likely as a result of the singular diet item animals were being hand-fed at the tourist sites. Similar results were noted in previous studies of stingrays in this area.² The long-terms effects of this type of diet on the health of southern stingrays in Grand Cayman is not well understood. Further investigation and continued sampling of this population of stingrays is ongoing.

Acknowledgements

The authors wish to thank Nicole Boucha, Nicole Hatcher, Lynda Leppert, Jessica Harvey, Alex Harvey, and Louisa Gibson for their assistance in the field and in the laboratory. The authors thank the Guy Harvey Ocean Foundation for financial support of this project.

*Presenting author

Literature Cited

1.  Cain DK, Harms CA, Segars A. 2004. Plasma biochemistry reference values of wild-caught southern stingrays (Dasyatis americana). J Zoo Wild Med. 35:471–476.

2.  Semeniuk CAD, Speers-Roesch B, Rothley KD. 2007. Using fatty-acid profile analysis as an ecologic indicator in the management of tourist impacts on marine wildlife: A case of stingray-feeding in the Caribbean. Environ Manage. 40:665–677.