title: Gauging the threat: the first population estimate for white sharks in South Africa using photo identification and automated software.
abstract: 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 the species has not made a marked recovery since being nationally protected in 1991. As such, additional international protection may prove vital for the long-term conservation of this threatened species.
authors.affiliation: Dyer Island Conservation Trust, Great White House, Kleinbaai, Gansbaai, South Africa.
authors.forename: Alison V
authors.initials: AV
authors.lastname: Towner
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Wcisel
authors.forename: Ryan R
authors.initials: RR
authors.lastname: Reisinger
authors.forename: David
authors.initials: D
authors.lastname: Edwards
authors.forename: Oliver J D
authors.initials: OJ
authors.lastname: Jewell
mesh_terms: D058500:Animal Fins / Q000033:anatomy & histology*; D000818:Animals; D003247:Conservation of Natural Resources / Q000379:methods / Q000706:statistics & numerical data*; D010781:Photography / Q000379:methods*; D011156:Population Density; D012754:Sharks / Q000033:anatomy & histology / Q000502:physiology*; D012984:Software; D013019:South Africa