Radio tagging of Franciscana dolphins in Argentina
Pablo Bordino, MSc, AquaMarina

Franciscana dolphins are among the smallest of dolphins, and are the most endangered dolphin species in South America. The main goals of this study were to determine if capture-release and radio-tagging of this species is feasible, and if so, to begin to obtain information regarding movement patterns to aid in development of an effective management plan in Argentina. Three female Franciscana dolphins were radio tagged with small VHF transmitters and released in Bahia Samborombon in March 2005. The tags were attached to the dorsal fins by a single delrin plastic pin with corrosible nuts. The dolphins were tracked for 6 weeks from a lighthouse, the roof of a hotel, a boat, and from the shore. The maximum range from the highest receiving stations was about 20 km. Signals were received from at least one of the tagged dolphins daily, from two individuals on 71% of days, and from all three individuals on 40% of the tracking days. Preliminary analyses by unit effort revealed fairly localized movements by the dolphins, which were mainly recorded in the same area where they were caught. Preliminary analyses suggest a movement pattern associated with the tidal flow, with dolphins coming into the bay during high tide. Though the pilot data set is small, the consistency of findings across the animals suggests that the current designation of a single management stock in Argentina should be re-evaluated. The suggestion of small ranges in areas of heavy artisanal fishing pressure increases the urgency with which protective measures need to be implemented for this species. This study represents the first time that radio tracking has been accomplished with Franciscana dolphins; additional tagging is planned for 2006. Support for this project was provided by Wildlife Trust, Disney Wildlife Conservation Fund, Disney’s Animal Programs, and the Chicago Board of Trade.