Gauging the Threat: The First Population Estimate for White Sharks in South Africa Using Photo Identification and Automated Software

Posted on: June 25th, 2013 by Hannah Darrin

South Africa is reputed to host the world’s largest remaining population of white sharks, yet no studies have accurately determined a population estimate based on mark-recapture of live individuals. We used dorsal fin photographs (fin IDs) to identify white sharks in Gansbaai, South Africa, from January 2007 – December 2011. We used the computer programme DARWIN to catalogue and match fin IDs of individuals; this is the first study to successfully use the software for white shark identification. The programme performed well despite a number of individual fins showing drastic changes in dorsal fin shape over time. Of 1682 fin IDs used, 532 unique individuals were identified. We estimated population size using the open-population POPAN parameterisation in Program MARK, which estimated the superpopulation size at 908 (95% confidence interval 808–1008). This estimated population size is considerably larger than those described at other aggregation areas of the species and is comparable to a previous South African population estimate conducted 16 years prior. Our assessment suggests

white shark fin

The drying fins from a white shark can be used for photo ID

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Citation: Towner AV, Wcisel MA, Reisinger RR, Edwards D, Jewell OJD (2013) Gauging the Threat: The First Population Estimate for White Sharks in South Africa Using Photo Identification and Automated Software. PLoS ONE 8(6): e66035. doi:10.1371/journal.pone.0066035