Establishing a Quantifiable Model of Whale Shark Avoidance Behaviours to Anthropogenic Impacts in Tourism Encounters to Inform Management Actions

Abstract

As the world's largest living fish, the whale shark has received much scientific attention in recent years, although despite this a great deal is still unknown on the life history and behavioural ecology of these majestic sharks. Whale shark related tourism has exploded in the last two decades from only a few sites in the 1990s to more than 12 sites internationally, allowing it to become a highly lucrative industry based upon this Vulnerable species. This study assesses the effects of anthropogenic impact on the sharks’ avoidance behaviours within modern day tourism encounters, and provides recommendations on how to control and reduce unnecessary disturbance to the species. By means of stereo-photogrammetry, continuous high definition videos of human-animal interactions were recorded and analyzed for behavioural changes against pre-selected independant variables. The use of Stereo-photogrammetry imagery also allowed for the accumulation of repeatable, proximity measurements of swimmer distance to the shark, permitting more precise and accurate results. Avoidance behaviours of 33 individual whale sharks were monitored during typical tourism encounters (n=75). A total of 192 search hours were documented over the collection periods, which incorporated three-aggregation sites spanning the Indian Ocean (the Seychelles, the Philipines & Mozambique). A generalized linear model demonstrated that proximity of swimmers to the shark was found to be significant (p=0.0295) in explaining the probability of the whale sharks showing disturbed behaviour. A proportional odds plot for proximity was developed to give an indication of the animals disturbance level in tourism interactions. At recommended distances of three metres from the sides of the shark, there is on average a 42% chance of disturbance, while at the distance of four metres from the tail area results showed a 31% chance of overall disturbance. The true estimate for either distance is likely to lie between 22-53% respectively with regards to the uncertainty around the mean predictions. Whale shark tourism is viewed as a potential means of protecting this threatened species, while also providing a sustainable livelihood for local communities and tourism providers. Management recommendations presented offer suggestions on how to tackle concerns over proximity distances and links to disturbance. Additionally judgments for future research endeavors into assessing both the impacts of uncontrolled tourism and participants behaviour.