“Biology, ecology and conservation of Mobulid rays in the Azores”

Mobulids are large migratory elasmobranchs, some of which appear to aggregate at specific locations and times. Due to their conservative life history traits, mobulids have low intrinsic capacity to sustain and recover from current threats globally, including directed fisheries, incidental capture, habitat destruction, pollution and unregulated tourism. Yet, although they are nowadays iconic species that support important ecotourism industries, most questions regarding their biology and ecology remain unanswered, hampering the identification and implementation of adequate conservation and management measures. This study provides an updated checklist of the family Mobulidae for the Azores, mid-North Atlantic, based on an extensive photographic, video and visual sighting database, and on the re-evaluation of previous citations for the region. There are, at least, three species of mobulids occurring in the Azores, possibly four: Manta birostris (occasional), Mobula tarapacana (seasonally frequent), and one or both of the Mobula mobular/M. japanica species complex (rare). This is the first study to provide detailed information on the spatial ecology of M. tarapacana across its circumglobal distribution. It demonstrates that, in the region, this species shows a marked preference for shallow seamounts, that some of these habitats support large and continuous aggregations of adults (Princesa Alice bank and Ambrósio reef), and that these aggregations seem to be restricted to the warmer months. A photographic database for mobulids and a program for the photo-identification of M. tarapacana based on ventral color patterns were also developed and implemented, in what constitutes the first and promising worldwide attempt to use photo-ID as a tool for Mobula demographic studies. Considering the highly migratory nature of these species and the current vulnerability of the most important, known aggregations sites, the findings in this study most possibly have direct implications for the conservation of the north Atlantic populations of Mobulas, in particular of M. tarapacana. Future research is urgent to learn more about the ecology and biology of the Mobulidae in the region and in the Atlantic.