Oceanic manta rays aggregating near a major population center have far higher injury rates than at an offshore protected area

Abstract

The oceanic manta ray Mobula birostris is an Endangered species facing numerous anthropogenic threats that have led to population declines worldwide. Although oceanic manta rays are fully protected in Mexico, this species is still threatened by bycatch and vessel collisions, which jeopardize the population’s stability and recovery. This study compares the prevalence and types of injuries observed in oceanic manta rays between the remote Revillagigedo Archipelago National Park and Bahía de Banderas, an area of high vessel traffic and small-scale fisheries in Mexico. Using visual censuses and photo-identification techniques conducted from 2014 to 2022 for Bahía de Banderas and from 1978 to 2020 for the Revillagigedo Archipelago, we found significant disparities in injury rates between the 2 regions. The overall injury rate was substantially higher in Bahía de Banderas (31.7%) than in the Revillagigedo Archipelago (5.2%), with a notable proportion of injuries attributed to anthropogenic causes, particularly vessel collisions and fishing gear entanglement. Moreover, the severity and types of injuries varied significantly, with a higher incidence of major injuries in Bahía de Banderas. These findings highlight the importance of marine protected areas for oceanic manta rays and emphasize the critical importance of implementing targeted conservation measures, especially in coastal regions with high maritime activity, to safeguard oceanic manta ray populations from further decline. We encourage the community and stakeholders to implement conservation actions urgently to preserve the vulnerable oceanic manta ray population in Bahía de Banderas and other coastal areas inhabited by this species.