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.