Manta munchies: plankton dynamics and feeding behaviour of reef manta rays (Mobula alfredi) around D’Arros Island in the Seychelles

The reef manta ray ( Mobula alfredi ) is a threatened filter-feeding elasmobranch that requires immediate management and protection across large parts of its range. Despite being well-studied, a detailed understanding of their feeding ecology, which shapes their residency, movement patterns, and behaviour, remains underexplored. Both global and site-specific research is required to fill significant knowledge gaps essential for designing effective conservation strategies for this species and their habitats. This study investigated M. alfredi feeding behaviour in relation to plankton biomass dynamics at D’Arros Island in the Seychelles, the largest known M. alfredi aggregation site in the country and a gazetted marine protected area. Plankton samples were collected, along with corresponding environmental data, during M. alfredi feeding and non-feeding behaviour. Statistical modelling revealed that surface feeding occurred predominantly during periods of higher plankton biomass, with a critical prey density threshold of 26.9 mg/m³, which had a significant relationship with tidal phase. Additionally, there were no significant differences in feeding behaviour and plankton biomass across seasons, which demonstrates the year-round value of D’Arros Island to this species. These findings provide new insights into the feeding ecology of M. alfredi in the Seychelles and support future conservation and management initiatives for this threatened species.