Acoustic telemetry reveals cross-border movements and conservation opportunities for reef manta rays Mobula alfredi in southern Africa

Reef manta rays Mobula alfredi occur across a range of protected and unprotected coastal habitats in the Southwest Indian Ocean, yet their movement ecology remains poorly understood in this region. In Mozambique and South Africa, reef manta rays have experienced significant declines, reflecting increasing pressures on regional populations. To better understand their spatial ecology and inform conservation strategies, we tagged 48 individuals with acoustic tags between 2022 and 2025 and tracked their movements between Mozambique and South Africa. Reef manta rays exhibited high residency within South Africa’s iSimangaliso Wetland Park, particularly in the Offshore Wilderness Zone, where strict protection and reduced human activity may provide refuge. In contrast, 90% of individuals detected in Mozambique were detected outside marine protected areas (MPAs), demonstrating the limited spatial protection available to reef manta rays in these waters. Approximately 30% of tagged individuals undertook transboundary movements, with the longest 1-way movement spanning 950 km and the longest round-trip totaling 1100 km between Mozambique and South Africa, highlighting the need for a coordinated regional conservation strategy. We recommend strengthening regional cooperation through harmonized fishing and trade regulations, improved enforcement capacity, and integration of reef manta rays into transboundary management frameworks to enhance protection for this vulnerable population. More broadly, our results emphasise the importance of cross-border management and equitable resource allocation to ensure the long-term conservation of migratory elasmobranchs in the Southwest Indian Ocean.