Beginning in the mid-1990s there has been an unprecedented increase in the numbers of dolphins using Sarasota Bay, from a 20-year average of about 100-120 dolphins to more than 175 dolphins in the early 2000’s. Some of this increase was a result of recruitment through successful reproduction of long-term residents, but many of the animals appeared in the bay as juveniles or adults, originating elsewhere. Because these “newcomers” rarely enter waters shallow enough to support our standard capture-release techniques, we conduct biopsy darting to obtain genetic samples for examination of mitochondrial DNA haplotypes and microsatellites, and to determine sex as part of our long-term program of monitoring population structure. Blubber obtained from the biopsy darting is analyzed for organochlorine contaminant concentrations. In combination, genetic and contaminant profiles may provide indications of the origins of the animals, allowing evaluation of a previously-undocumented mechanism for variation in dolphin population structure.
Since 2003, 58 biopsy dart samples have been obtained from bottlenose dolphins that have not been previously handled during health assessments. Samples have been primarily collected from mid-Sarasota Bay but have extended from the Manatee River to Venice Inlet. Genetic analyses of these samples are currently being run by Dr. Debbie Duffield of Portland State University. Contaminant samples have been banked at the National Institute of Standards and Technology in Charleston, SC. In addition to the principal goal of collecting skin and blubber from previously unsampled individuals, over the years this project has trained a number of US and foreign researchers in the practice of biopsy sample collection and processing.