Shark Identikits

Shark Identikits

The use of dorsal fin photo-identification methods

White sharks (Carcharodon carcharias) and bronze whaler sharks (Carcharhinus brachyurus) are threatened marine species. To adequately monitor these marine predators, there is a need for data-driven decision making. To overcome challenges associated with marine data collection, photo-ID methods obtained from tourist boats offer an easy alternative to study these animals. Photo-ID is based on photographing species’ natural markings that enable individual identification such as the notches pattern on a white shark’s primary dorsal fin. Various methods exist to catalogue photo-ID data, but standardisation is a key component to apply them at a national and global level. Our study shows how computer-assisted matching software, Identifin, can outperform manual matching methods by being faster, and by maintaining the highest matching accuracy (and lowest error rate) irrespective of the size of the photographic database. We also show for the first time how the dorsal fin notches patterns can be used to differentiate between bronze whaler shark individuals, and how the photo-ID method alongside the Identifin software, can be used to estimate shark population numbers. Computer-assisted matching presents the potential to standardise photo-ID data cataloguing and to generate comparative outputs, across multiple regions where large sharks aggregate. Using standardised methods will facilitate collaborative research and the implementation of efficient conservation strategies.

ABOUT MEGAN MAROEN

Megan is the senior marine biologist at White Shark Diving Company/ Shark and Marine Research Institute. She completed her MSc in Zoology, at Stellenbosch University, on the use of the photo-identification method on white sharks and bronze whaler sharks in Gansbaai, and continues to collect data from the shark vessels to monitor population changes within the bay.

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