Automated Visual Fin Identification of Individual Great White Sharks

This paper discusses the automated visual identification of individual great white sharks from dorsal fin imagery. We propose a computer vision photo ID system and report recognition results over a database of thousands of unconstrained fin images. To the best of our knowledge this line of work establishes the first fully automated contour-based visual ID system in the field of animal biometrics. The approach put forward appreciates shark fins as textureless, flexible and partially occluded objects with an individually characteristic shape. In order to recover animal identities from an image we first introduce an open contour stroke model, which extends multi-scale region segmentation to achieve robust fin detection. Secondly, we show that combinatorial, scale-space selective fingerprinting can successfully encode fin individuality. We then measure the species-specific distribution of visual individuality along the fin contour via an embedding into a global `fin space'. Exploiting this domain, we finally propose a non-linear model for individual animal recognition and combine all approaches into a fine-grained multi-instance framework. We provide a system evaluation, compare results to prior work, and report performance and properties in detail.Comment: 17 pages, 16 figures. To be published in IJCV. Article replaced to update first author contact details and to correct a Figure reference on page

Demographics of a seasonal aggregation of white sharks at Seal Island, False Bay, South Africa

Includes bibliographical references.White sharks (Carcharodon carcharias) are widely distributed, ecologically important marine apex predators that are considered to be vulnerable to extinction. Given their crucial roles in structuring marine ecosystems, their populations need to be effectively monitored. Photo-identification provides a standardised, non-lethal method of assessing the population dynamics of extant species and provides live-encounter mark-recapture and data that are essential for management and conversation. White sharks occur throughout South African coastal waters but their centre of abundance is the Western Cape, where large sharks predominate at aggregation sites like Seal Island, False Bay. This study documents inter- and intra-seasonal trends in mean sighting rates and sex ratios of white sharks at Seal Island, and provides mark-recapture data that are used to estimate proportions of "resident" and "transient" white sharks, their size-distribution and maturity composition

Behavioural responses of white sharks to specific baits during cage diving ecotourism

This study describes the effect of different baits on the attraction, surface behaviour and conditioning of white sharks Carcharodon carcharias during local ecotourism activities. The sightings, behaviours, and pictures used for photographic identification were obtained during August to November 2012-2014 onboard tourist boats in Guadalupe Island, Mexico. Four types of baits were used: (1) frozen bait; (2) frozen bait and natural chum; (3) fresh fish bait; and (4) mackerel bags. Data were analysed according to sex, maturity and the total of sharks using 6,145 sightings of 121 white sharks. The type of bait showed no significant difference on the effectiveness to attracting sharks. Ethological analysis showed that the type of bait had a significant effect on the shark's surface behaviour during its interactions with boats. Natural chum and fresh baits showed short term behavioural patterns constituted by increased number of violent interactions with the bait, while the frozen bait did not generate a defined behavioural pattern. Conditioning of white sharks was determined by the number of interactions and the consumption frequency of the bait. Fifty nine percent of sharks (n=41) showed no conditioning, 36% (n=25) showed a low risk and only 5% (n=3) were found to have a high risk of conditioning. The results suggest that current ecotourism has no effect on the conditioning of the white sharks, and that all baits have a similar effectiveness for attracting the sharks. However, a different behavioural pattern was observed when fresh bait and chum were used, which could increase the potential of accidents during ecotourism

Monitoring fisheries within the Reef 2050 Integrated Monitoring and Reporting Program: final report of the fisheries expert group

This report provides a suite of recommendations for monitoring fishery systems as part of the Reef 2050 Integrated Monitoring and Reporting Program (RIMReP). These recommendations were based on a desktop analysis of peer-reviewed literature, technical reports and other scientific publications, expert knowledge and advice from members of the various RIMReP Expert Groups and outcomes from a series of workshops and meetings