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Release and follow-up monitoring of Risso's dolphin "Clyde": Record movements and dives
By Randall S. Wells, PhD
 Risso's dolphin "Clyde" at Mote's Dolphin and Whale Hospital.
During 2006, the Sarasota Dolphin Research Program, in collaboration with Mote Marine Laboratory’s Dolphin and Whale Hospital, had the opportunity to learn about the movement and dive patterns of a species of deep-water dolphin for which little information was previously available. On July 16th, 2005, five Risso’s dolphins, Grampus griseus, stranded near Marco Island, Florida. Two of these, an adult male "Clyde" and an adult female “Bonnie,” were transported to Mote’s Dolphin and Whale Hospital. They were treated for severe pneumonia, as well as a variety of other conditions, including elevated white cell counts and elevated liver enzyme levels. Unfortunately, Bonnie, who was determined to be pregnant several months after arriving at the hospital, did not survive. Clyde was tagged with a satellite-linked radio transmitter and was released about 115 miles offshore of Sarasota on February 10th, 2006. The release was planned to return Clyde to the appropriate deep water habitat nearest to Sarasota, in order to reduce transport time. Clyde was tracked for 23 days, as he moved from the Gulf of Mexico to a deep trench just north of Cuba, then continuing northward in the Atlantic Ocean to the waters offshore of Delaware (see map below). Most of Clyde’s dives were to depths of less than 100 meters, but some were to 400-500 meters, and were of up to 10 minutes in duration. To the best of our knowledge, these are the deepest dives ever recorded for this species. Clyde’s last transmissions showed him to be in typical habitat for the species, and in the same general area where a rehabilitated Risso’s dolphin released by Riverhead Foundation in New York had been tracked during 2005.
Clyde’s release resulted from the dedicated efforts of many volunteers through Mote’s Dolphin and Whale Hospital. Tagging and tracking were supported by the J.H. Prescott Marine Mammal Rescue Assistance Grant Program.
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