Spatio-temporal patterns, trends, and oceanographic drivers of whale shark strandings in Indonesia

Despite the increased international attention to whale shark conservation, their populations remain predominantly depleted due to anthropogenic activities such as fishing, ship collisions, and marine pollution. Reports of whale shark strandings in Indonesia have been increasing in recent years, elevating concerns regarding their well-being and the potential disturbance to their population recovery. However, limited understanding of stranding patterns, trends, and the oceanographic factors potentially driving these events has resulted in efforts focusing primarily on responding to strandings rather than implementing effective mitigation strategies. Using a 13-year stranding dataset (n = 115) obtained from open-access databases, reports, news, and publications, we examined the characteristics of stranding cases in Indonesia, including population demographics, where hotspots occur, and whether their occurrence is related to oceanographic dynamics in the region. Our study highlights significant population-level disturbances, with 70% of stranded individuals being large juveniles (4-7 m). It also documented a positive interannual trend in stranding cases (R² = 0.67, p < 0.01). The southern coast of Java has emerged as a stranding hotspot, with events seasonally associated with strong upwelling, likely related to the seasonal foraging activities of whale sharks in the region. Although natural events were identified as the main factors contributing to whale shark strandings, anthropogenic activities may also play an important role and require further investigation.