A novel categorisation system to organise a large photo identification database for white sharks<i>Carcharodon carcharias</i>

Andreotti, Sara; Rutzen, Michael; Wesche, PL; O'Connell, CP; Meÿer, Michael A.; Oosthuizen, Herman; Matthee, Conrad A.

doi:10.2989/1814232x.2014.892027

Cited by 10 publications

(37 citation statements)

References 35 publications

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“…As body pigmentation and markings on C . carcharias can change, a long‐term identification technique, such as dorsal‐fin photo‐identification, is warranted to aid in non‐invasively assessing shark growth over multiple years (Robbins & Fox, ; Andreotti et al , ). Furthermore, the addressed methods of stereo‐photogrammetry are deployed on schooling fishes and use two separate remote cameras at a fixed distance from each other.…”

Section: Discussionmentioning

confidence: 99%

“…and water were used to attract C . carcharias towards the vessel (Laroche et al , ; Andreotti et al , ). A high‐resolution photograph of a C .…”

Section: Methodsmentioning

confidence: 99%

“…A high‐resolution photograph of a C . carcharias dorsal fin was obtained using a 70–300 mm lens mounted on another DSLR camera to permit individual shark identification (as described in detail by Andreotti et al , ). In addition to photo‐identification and to maximize identification success across subsequent trips, additional C .…”

Section: Methodsmentioning

confidence: 99%

“…g . a shark cage or vessel), but this technique can yield inaccurate results (Anderson et al , ; Andreotti et al , ). Carcharodon carcharias populations are constantly threatened by anthropogenic mortality, and the lack of knowledge regarding their population status and migratory nature is the greatest obstacle to effectively implement conservation measures.…”

Section: Introductionmentioning

confidence: 99%

“…Carcharodon carcharias populations are constantly threatened by anthropogenic mortality, and the lack of knowledge regarding their population status and migratory nature is the greatest obstacle to effectively implement conservation measures. Therefore, in this study, a non‐invasive technique that combined dorsal‐fin photo‐identification (Andreotti et al , ) with parallel laser photogrammetry (Rohner et al , ) was implemented on free‐ranging C . carcharias in Gansbaai, South Africa.…”

Section: Introductionmentioning

confidence: 99%

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Risks and advantages of using surface laser photogrammetry on free‐ranging marine organisms: a case study on white sharks Carcharodon carcharias

Leurs

O'Connell

Andreotti

et al. 2015

Journal of Fish Biology

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This study employed a non-lethal measurement tool, which combined an existing photo-identification technique with a surface, parallel laser photogrammetry technique, to accurately estimate the size of free-ranging white sharks Carcharodon carcharias. Findings confirmed the hypothesis that surface laser photogrammetry is more accurate than crew-based estimations that utilized a shark cage of known size as a reference tool. Furthermore, field implementation also revealed that the photographer's angle of reference and the shark's body curvature could greatly influence technique accuracy, exposing two limitations. The findings showed minor inconsistencies with previous studies that examined pre-caudal to total length ratios of dead specimens. This study suggests that surface laser photogrammetry can successfully increase length estimation accuracy and illustrates the potential utility of this technique for growth and stock assessments on free-ranging marine organisms, which will lead to an improvement of the adaptive management of the species.

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Section: Discussionmentioning

confidence: 99%

“…and water were used to attract C . carcharias towards the vessel (Laroche et al , ; Andreotti et al , ). A high‐resolution photograph of a C .…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Risks and advantages of using surface laser photogrammetry on free‐ranging marine organisms: a case study on white sharks Carcharodon carcharias

Leurs

O'Connell

Andreotti

et al. 2015

Journal of Fish Biology

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Testing the exclusion capabilities and durability of the Sharksafe Barrier to determine its viability as an eco‐friendly alternative to current shark culling methodologies

O’Connell¹,

Andreotti

Rutzen³

et al. 2017

Aquatic Conservation

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1. Following a shark attack, local governments often rapidly respond by implementing indiscriminate shark culls. These culls have been demonstrated to have substantial localized and adverse effects on a variety of marine organisms, and therefore there is an increasing need for an ecofriendly alternative that maximizes both beachgoer and marine organismal safety.2. In response to such culls, the novel magnetic barrier technology, the Sharksafe Barrier was developed and rigorously tested on a variety of sharks implicated in shark attacks (e.g. bull sharks -Carcharhinus leucas and white sharks -Carcharodon carcharias). Although these studies exhibited promise in shark swim pattern manipulation and C. leucas exclusion, research was lacking in assessing if the technology could serve as an alternative to shark nets, or more specifically, if it could exclude motivated C. carcharias from bait.3. Using a 13 m × 13 m square exclusion zone, this study aimed to test the C. carcharias exclusion capabilities of the Sharksafe Barrier while additionally assessing the long-term structural integrity of the system. 4. After 34 trials and approximately 255 hours of total video collected over two years, data illustrate that all interacting C. carcharias were successfully excluded from the baited Sharksafe Barrier region, whereas teleosts and other small elasmobranch species were not. In addition, the long-term deployment potential of this barrier system held promise owing to its ability to withstand harsh environmental conditions. 5. Therefore, with the successful exclusion of a second large shark species, C. carcharias, from a baited region, continued long-term research and implementation of this system at other locations should be considered to assess its viability and overall success as a bather and shark protection system.

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The effectiveness of the semi‐automated Identifin software to accurately fast‐track dorsal fin photographic identifications of sharks

Maroen,

Rowlinson,

Matthee

et al. 2024

Aquatic Conservation

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For some marine species, photo‐identification (photo‐ID) data can be used to generate population estimates critical for conservation efforts. For the white shark (Carcharadon carcharias), different photo‐ID methods have been proposed: (1) the traditional manual matching method based on non‐organized databases, (2) the notches code method based on organized databases and (3) the semi‐automatic software, Identifin. However, the effectiveness of these different methods and the applicability to other shark species have not been adequately explored. Eleven inexperienced and two experienced investigators used the three different photo‐ID methods to record the accuracy and time taken to identify individual white sharks from photo‐ID images. Both the traditional and notches code methods allowed for the accurate matching of individuals to the databases provided. For all investigators, the notches code method used significantly less time (14 min ± 0.14 min) than the traditional matching method (19 min ± 1.34 min). The semi‐automated method, Identifin, further shortened the identification time to 2 min (± 0.10 min) and provided a significantly higher matching accuracy (96% correct matches) compared with traditional manual matching (78% correct matches) and the notches code method (70% correct matches). The use of Identifin was tested to identify bronze whaler sharks (Carcharhinus brachyurus), a species with finer notches patterns when compared with white sharks. Identifin showed less efficiency in matching individual photographs to the database, but when very‐high‐quality (VHQ) photographs were available, matching improved substantially. Identifin software shows great potential in assisting researchers to accurately identify individual sharks in large databases, and this can contribute significantly to the conservation of shark species. The software and automated process need to be adapted to be functional on a variety of different shark species, but it proves to be an effective tool in managing large photo‐ID databases.

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A novel categorisation system to organise a large photo identification database for white sharksCarcharodon carcharias

Cited by 10 publications

References 35 publications

Risks and advantages of using surface laser photogrammetry on free‐ranging marine organisms: a case study on white sharks Carcharodon carcharias

Risks and advantages of using surface laser photogrammetry on free‐ranging marine organisms: a case study on white sharks Carcharodon carcharias

Testing the exclusion capabilities and durability of the Sharksafe Barrier to determine its viability as an eco‐friendly alternative to current shark culling methodologies

The effectiveness of the semi‐automated Identifin software to accurately fast‐track dorsal fin photographic identifications of sharks

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