Underwater photo-identification of sicklefin lemon sharks, negaprion acutidens, at Moorea (French Polynesia)

Shark feeding is a controversial recreational activity that may alter shark behaviour. In order to investigate possible behavioural changes at the level of the individual, it is necessary to recognise each shark underwater and in a nonintrusive way. In this study, we tested a protocol based on natural marks on fins, and coloured spots and scars on the body to differentiate individual sicklefin lemon sharks. We found that a feeding group, aggregated for 26 months at a northern location off Moorea Island, comprised 32 animals (19 females and 13 males), identified from 2589 observations made over 541 dives. Post-dive photo-identification of individual sharks was a reliable technique, whereas a high level of skill was required to ensure an instantaneous identification underwater. However, direct underwater identification of individual sharks can be of potential use in shark behavioural studies.