Biodiversity and conservation of elasmobranchs in the Mascarene Islands: Policy implementation and protection strategies

Although the Mascarene Archipelago is considered one of the main marine biodiversity hotspots in the Indian Ocean, the elasmobranch species residing in these waters remain poorly understood. It is crucial to fill these information gaps to better inform actions for their conservation and management. The Mascarene Archipelago Elasmobranch Observatory (MAEO) program established an elasmobranch sighting network involving several ocean user groups across Réunion, Mauritius and Rodrigues islands. Additionally, active searches on social media contributed to an increase in elasmobranch observations. In parallel, remote underwater video systems (both baited and unbaited) and underwater visual census surveys were performed. From 2021 to 2024, 1615 elasmobranch sightings were reported, including two species newly recorded for Réunion, one for Mauritius, and one species new to science. Of the 67 elasmobranch species known in the Mascarenes (updated list from this study), 32 species (47.8 %) were recorded in this study. Among the total 67 species, 42 (62.7 %) are classified as threatened with extinction according to the IUCN Red List of Threatened Species. A review of current legislation in Réunion and Mauritius indicates that while some regulations exist to protect elasmobranchs, they are often poorly understood or inadequately enforced. Strengthening and enforcing fishing regulations is crucial. Moreover, raising public awareness and education is key to enhancing elasmobranch protection. Considering this, significant efforts have been made to promote the MAEO program and engage the public across the region. After three years, the findings provide useful information to inform effective conservation measures for elasmobranchs in the Mascarenes. Simultaneously, the results underscore the need for further research on these species in this region.