AN IDENTIFICATION STUDY ON BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN NORTHEAST PATAGONIA, ARGENTINA

In Argentina, bottlenose dolphin (Tursiops truncatus) sightings decreased notably since the late 80s in regions where it used to be frequent to observe them. Nowadays, Northeast Patagonia is one of the few regions where they still can be seen frequently, although local increasing human activities result in increasing need for information. In general, photo-identification has been established as a helpful tool in cetacean research. However, only few studies have applied this method to bottlenose dolphins in Argentina. This study is therefore aimed to obtain basic information concerning bottlenose dolphins through their identification, this way contributing to their conservation. Land-based observations were made in the northern Gulf of San Matías, Patagonia, Argentina, from August 2006 up to June 2008. Over 15.000 digital pictures of dorsal fins were analysed using the computer assisted identification systems FinEx and FinMatch. Dolphins re-identified during all four seasons in one year were defined as residents. The degree of residency was further estimated by the re-identification frequency (RF); non-resident (RF=1-3) - occasional (RF=4-7) - frequent (RF=8-11) - common (RF¿12). In total, 221 surveys were conducted with an average observation effort of 3.2h per survey, resulting in a total observation effort of 915h of which 124h were spent with 182 dolphin groups. A total of 50 dolphins were identified of which the vast majority (82%) was photographed only in the Natural Protected Area Bahía San Antonio (NPABSA), due to the higher observation effort in this region. Nevertheless, 12% of the catalogued dolphins could be photographed in both NPABSA and the Río Negro estuary, indicating that their home-range might include at least the whole northern region of the Gulf San Matias. Dolphins could be re-identified up to 13 days with 54% showing a degree of residency for NPABSA. This study shows the first data concerning bottlenose dolphins in Northeast Patagonia, but further investigation is highly necessary to improve their conservation. Therefore, the obtained photo-identification catalogue from the presented study is meant to serve as a primary tool for progressing research concerning this species in Argentina