Assessing the impacts of tourism on the world's largest fish Rhincodon typus at Panaon Island, Southern Leyte, Philippines

1. Shark-based tourism is a rapidly growing industry, particularly with whale sharks, as new hotspots are identified worldwide. Understanding any impacts of tourism is essential to minimize any potential detrimental effects on the target species and habitat. 2. In-water behavioural observations of whale sharks were used to understand any impacts of tourism at a small site in Panaon Island, Southern Leyte, Philippines. A generalized linear mixed model was fitted to test anthropogenic and environmental variables, with interaction duration as the response variable, to assess any disturbance to the animals by the tourism activities. 3. Whale sharks were observed between the months of November and June between 2013 and 2016, with highly variable seasons. In total, 527 tourist-whale shark interactions were recorded during 359 trips identifying 104 individual whale sharks, most of which were juvenile males (85%, measuring c. 5.5m total length). Proximity of motorized vessels and interactions in deeper waters were found to significantly shorten interactions. Short-term behavioural changes were observed in response to human events (e.g. touching). Interactions when whale sharks were feeding were significantly longer than when they were not. Individual behavioural variability was observed. 4. Impacts could be mitigated with small managerial changes and increased enforcement, such as limiting the number of motorized vessels and the number of people around the whale sharks. Although no long-term impacts were recorded during this study, it is difficult to ascertain this in a long-lived, wide-ranging species. 5. This knowledge gap highlights the need to build long-term monitoring programmes, and to apply the precautionary principle for the sustainable use of this endangered species.