This paper describes a standardised and efficient technique for analyzing and cataloging the dorsal fin of bottlenose dolpins. Dorsal fins are photographed with a 400mm lens mounted on a 35mm camera equipped with a high speed motor drive. The resulting black and white negatives are sorted into clear duplicates of recognisable dorsal fins, and the best photograph of each individual is traced to uniform size on white paper. A ratio is then computed by dividing the distance between the two largest notches by the distance of the larger lower notch to the top of the fin. Tracings are organised by this dorsal ratio within four catalogs: (a) single notches; (b) top notches; (c) two or three notches; (d) four of more notches. Newly traced fins are compared to previous tracings in the appropriate catalog with similar dorsal ratios. In the absence of a resighting, tracings in all catalogs are inspected. Tentative resightings are confirmed by visual inspection of the original negative with an 8x loupe. A computer program stores, analyses and displays photographic sighting and resighting data.
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