Spatial Ecology of the Population of Reef Manta Rays, Mobula alfredi (Krefft, 1868), in New Caledonia Using Satellite Telemetry 1–Horizontal Behaviour

The reef manta ray (Mobula alfredi) is a highly mobile and plankton-feeding species, classified vulnerable to extinction on the IUCN Red List for Threatened Species. Knowledge on their spatial ecology and the extent of their dispersal remain incomplete, especially within island-fragmented habitats as found in New Caledonia. Satellite telemetry was used to investigate the horizontal movement ecology of reef manta rays in New Caledonia. A total of 21 manta rays were tagged with pop-up satellite archival transmitting tags (21 Fastloc and 2 MiniPAT) that remained deployed for a duration ranging from 3 to 180 days (mean ± SE = 76.7 ± 50.3). Rays presented a strong site fidelity and an important affinity for coastal waters. Long-distance migrations (> 300 km) were also observed, mainly through coastal and shallow water paths. Horizontal movements were compared to a home range area and classified into four distinct patterns: Fidelity, Excursion, Fidelity + Relocation and Relocation. The most dominant pattern was Fidelity where manta rays remained within their home range for the whole duration of the tag deployment. Our findings may assist the design of more appropriate management strategies for the species in New Caledonia and other regions worldwide.