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Identifying dolphins using photos of the unique pigment patterns on their fins can be used to help in the management of a species.

Cetacean biologist Dr Krista Hupman from NIWA is a lead author of two 2018 scientific papers outlining an accurate method of counting dolphins by using photo identification. “We have photographed individual dolphin’s dorsal fins and established a catalogue of dolphins that can be differentiated by differences in their dorsal fin edge markings and pigmentation patterns,” Dr Hupman says.

Scientists use catalogues of animals to determine how many animals occupy a region and such information can be used to determine if the population is in decline.

However, some dolphins can be hard to count as they occur in large populations, over vast areas and may lack distinctive markings for identification. It is for these reasons that many scientists shy away from using photo-identification to conduct population estimates, and instead use aerial or shipboard surveys.

“It’s really hard to know how many dolphins there are of some species, because they travel over large distances and don’t have any distinctive markings. We’ve developed a reliable photo-identification method that challenges how dolphins are counted that could have significant impact on the management of these animals.”

Fin edge and patterns the key to id

Dr Hupman says that ecologists should consider the use of photo-identification for generating population estimates for large populations of poorly marked dolphins and that the methods described in the two papers could be implemented for similar animal populations worldwide.
The first step was applying an algorithm to classify individuals based on their pigmentation patterns alone, which has resulted in a much faster and efficient system for cataloguing individuals.
“It used to take up to an hour to compare one dolphin image to the entire catalogue of individuals. However, by using these algorithms we can match an image to the catalogue in a matter of seconds”.

The next stage involves streamlining how photographs are processed by reducing the amount of time required to crop and rotate images so they can be compared to the catalogue. Hupman and her colleagues have developed an online tool to assist with this process called Photoid Ninja. It is now being used by cetacean scientists from the US National Oceanic and Atmospheric Administration (NOAA).
This work is part of an ongoing collaboration with Massey University researchers Dr Matthew Pawley, Dr Andrew Gilman and Dr Karen Stockin which aims to optimise the use of individual identification for the estimation of abundance.

Fin ID examples of Common Dolphins

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