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Satellite Tag Study Reveals Importance of Philippine Waters for Whale Sharks

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Satellite tag tethered to one of the whale sharks (Photo: Gonzalo Araujo/LAMAVE Press)

A new scientific study published in PeerJ – the Journal of Life and Environmental Sciences has tracked juvenile whale sharks across the Philippines, emphasising the importance of the archipelago for the species. The study is the most complete tracking study of whale sharks in the country, with satellite tags deployed on different individuals in multiple sites.

The Philippines is an important hotspot for whale sharks and is home to the third largest known population of the world's largest fish. Although whale sharks have received protected status in the Philippines since 1998, the IUCN categorised the species as 'endangered' in 2016 as a result of a population decline of more than 50 per cent, largely the result of the continued exploitation of whale sharks in the Indo-Pacific region. Concerns for the future of the giant sharks remain, particularly in South East Asia, due to continued fishing in regional territories. Understanding the movements of whale sharks in the Philippines is therefore vital in order to identify conservation priorities for the species

By attaching Wildlife Computer SPOT5 satellite tags to whale sharks, researchers from Large Marine Vertebrates Research Institute Philippines (LAMAVE), Marine Megafauna Foundation (MMF) and Tubbataha Management Office (TMO) were able to follow the movements of juvenile whale sharks in near real-time to gain an insight into their behaviour. The tags work by communicating with passing ARGOS satellites, transmitting a location when the tags' sensors are triggered every time a tagged whale shark breaks the surface. In order to assist with a successful, the tags were tethered to the whale sharks by a 1.8m line to ensure the tags broke the surface as frequently as possible.

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Overhead view of a tagged whale shark (Photo: Gonzalo Araujo/LAMAVE Press)

Seventeen individual whale sharks were tagged in three different locations in the Philippines: Panaon Island (Southern Leyte), northern Mindanao (Misamis Oriental and Surigao del Norte) and Tubbataha Reefs Natural Park (Palawan). Tagging took place between April 2015 and April 2016 and all of the tagged whale sharks were juveniles, ranging in size between 4.5 – 7m  with 73 per cent being male.

In the peer-reviewed paper, the researchers discovered that all the tagged whale sharks stayed within the Philippines during the tracking period, emphasising the importance of the archipelago for the species. The longest track observed was from a whale shark originally tagged in Tubbataha Reefs Natural Park, which appeared to swim through the Sulu and Bohol Seas and into the Pacific, a journey of over 2,500 km in length. While whale sharks are not known for their speed, results revealed that one individual whale shark was averaging 47km a day, a clear demonstration of the mobile nature of the species.

Lead author of the study, Gonzalo Araujo stresses that the research 'highlights the high mobility of whale sharks, even juveniles, and the need for broader scale management and conservation plans for this endangered species.'

Dedicated research by LAMAVE and citizen science has identified more than 600 individual whale sharks in the Sulu and Bohol Seas, yet the proximity of this population to fisheries in the broader region of the South China Sea means it is vital to monitor the population as a whole in order to understand if this particular population is in recovery or continuing to decline. Identifying threats and mitigation strategies is a conservation priority for the species. LAMAVE continues to study whale sharks in five key areas in the Philippines, working with local and national governments as well as collaborating organisations to develop conservation strategies for this iconic species.

 

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