Pelagic sharks are poorly understood because of limitations inherent in studying them in situ. Knowledge that pelagic thresher sharks (Alopias pelagicus) regularly visit specific locations in the Philippines presented an unique opportunity to study new aspects of their behaviour and biology, and promote their conservation in the region.
Post-mortem examinations were conducted on 11 dead A. pelagicus specimens to investigate their ontogenic growth trends, and ectoparasite attachments.
Remote and handheld video was used to directly observe pelagic thresher sharks in situ at two sites in the central Visayas. From 239 video observations of pelagic thresher sharks, 117 behaviour events were analysed. 101 individual A. pelagicus were identified by using allometry to non invasively assess shark maturity from video still images, and by tabulating physical characteristics that were unique to each shark.
Understanding new aspects of the behaviour and biology of pelagic thresher sharks led to their legal protection in many parts of the Philippines, and provided insight into managing tourism activities at sites where they forage and clean.
Observable behaviours seen at these sites may explain why these mainly oceanic sharks venture into shallow coastal waters where they are vulnerable to anthropogenic disturbance.
Dr Simon Oliver from University of Chester joins us at SciBar to present on this topic.
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