Assessing and Mitigating Humpback Whale (megaptera Novaeangliae) Disturbance of Whale-watching Activities in Reunion Island

Whale watching, including swim-with-whales activities, is developing at an enormous rate in Reunion Island. This is raising concerns about its impacts on breeding humpback whales and challenging the sustainability of the activity. In 2017, a dedicated-at-sea patrol team, "Quiétude," was created to observe, monitor, and raise awareness to the whale watchers in order to improve compliance with local guidelines. In this context, the team assessed whale watching in Reunion Island during two humpback whale breeding seasons in 2017 and 2018, between June and October. Sighted groups were mostly composed of mother/calf pairs spending most of their time resting near or at the surface. Whale-watching vessels were present in 85.1% of sightings, of which 68.4% were recreative. Swimwith-cetaceans activities were very frequently observed in 42% of sightings. Overall, compliance with the charter was as high as 68% of whale sightings with vessels/swimmers were in line with the recommendations. However, low compliance (32.8%) was observed with the specific recommendations of swim-with-cetaceans activities. Swimmers were reported in surface active groups displaying agonistic behaviors, which poses evident human safety concerns. Humpback whale resting behaviors were disrupted significantly by whale-watching activities. Humpback whales tended to avoid vessels and swimmers, especially when their behavior was intrusive or not compliant with the charter. Positive humpback whale responses were more likely to occur if the charter's recommendations were not breached. Our results highlight how a nonbinding regulation, with recommendations scrupulously pursued, allows for a reduction in whale-watching disturbances and supports a better tourism experience. Our results advocate for reinforcing tourism education, whale-watching adaptive management and regulations, specifically for vulnerable groups with a calf, and for the swim-with-whales activities. This could be efficiently achieved by engaging all stakeholders and the permanent team on the field "Quietude" to enhance dissemination of best practices and sensitivity around sustainable values of implemented regulations.