Last week the CEI Elasmobranch Research Team took a trip to the beautiful islands of the Exumas in search of southern stingrays (Hypanus Americanus). This chain of hundreds of small islands and cays is just one of the sampling sites for postgraduate student Tanja Schwanck’s Masters’ thesis project which is investigating the gene flow between subpopulations of southern stingrays across several locations in the central Bahamas. This project requires the sampling of rays in a variety of places, from the creeks of North Eleuthera to the shores around Bimini nearly 200 miles away. Tanja will use the genetic samples collected from the different sites to determine the genetic connectivity between the subpopulations of rays.
The team set off for the Exuma Cays just as the sun was rising and began the near 2 hour journey across the Exuma Sound. About an hour in to the boat ride, they were greeted by a large pod of bottlenose dolphins. Just a few minutes later, someone noticed more dorsal fins poking out of the waves and they realised there were several short-fin pilot whales gliding in the wake of the boat! Everyone was amazed by the huge and graceful mammals but they had to continue to chase the islands they could finally see on the horizon.
They arrived at the chain of islands and headed straight for their first location, Ship Channel Cay. Patrolling the creek, they saw several sizeable Caribbean whiptail stingrays (Styracura schmardae) but no sign of any southern stingrays. The team took the boat to the next island, Norman’s Cay, and circled around the shoreline, inspecting the shallow waters. They came across a large southern ray and followed it in the boat, trying to coax it closer to the shoreline, where they could encircle and catch it. After about an hour of following it, the ray remained in the deeper waters, too deep for the team to stand a chance of catching it. They decided to cut their losses and try another location.
After lunch they drove north to Long Cay, where stingrays are known to commonly hang out near the shore. Scouting the shallows around the coast of the island, they finally came across a familiar looking diamond shaped shadow near the shore, which they instantly recognised as a southern stingray. The team sprang into action, hopping off the boat and encircling the ray and herding it into the seine net and eventually scooped it into a dip net. They wrapped the tail and barb of the ray, took measurements and biological samples and released it, all within a few minutes. The team watched the ray dart off into deeper water and climbed back on the boat. Tanja and her team returned to campus in time for dinner, exhausted but satisfied with another ray added to the CEI stingray research database.