Behavioral responses of whale sharks to fishing intensity Reduction: Implications for fishery management and megafauna conservation

Abstract

Understanding how marine megafauna respond to human activity changes is challenging but essential for effective conservation and management. Using China's summer fishing moratoria and the COVID-19 lockdown as quasi-natural experiments, we aimed to investigate whether temporal reductions in fishing activity affect the occurrence of whale sharks (Rhincodon typus) in Chinese coastal seas. We compiled occurrence records from social media platforms (2016–2023), standardized them by fishing effort data derived from Global Fishing Watch, and validated findings through interviews with local fishers. Our analysis revealed that both the summer moratoria and the COVID-19 lockdown significantly reduced fishing intensity, with moratoria having a stronger effect. Standardized whale shark occurrences increased significantly during summer moratoria, suggesting behavioral return to coastal foraging grounds in response to predictable, high-magnitude reductions in human disturbance. However, no comparable effect was detected during the COVID-19 lockdown. These findings highlight the role of disturbance magnitude and temporal predictability in shaping marine megafauna behavior. Additionally, the occurrences from social media also renewed the IUCN range map and suggested some foraging sites of whale sharks in China's seas. We recommend targeted protection at seasonal foraging sites during summer moratoria and adaptive spatial management to mitigate bycatch risks in China's seas. Our study highlights the utility of integrating social-media sightings and local ecological knowledge to assess the behavioral response of marine megafauna to policy interventions, and to monitor spatio-temporal dynamics of rare and iconic marine megafauna at large spatial extents.