August 2020

Just off the northeastern corner of Yucatan’s Peninsula, the Mexican Caribbean Biosphere Reserve (MCBR) is an important aggregation site for filter-feeding elasmobranchs during the summertime. Hundreds of whale sharks (the biggest fish in the ocean!) and oceanic manta rays can be seen seasonally in these waters feasting on abundant zooplankton blooms. During the first few days of August, we were lucky enough to visit this site during our research trips and find huge numbers of beautiful manta rays and magnificent whale sharks!

Large aggregations of oceanic mantas (Mobula cf. birostris) off the Mexican Caribbean this month. — Large aggregations of oceanic mantas (*Mobula cf. birostris*) off the Mexican Caribbean this month.

Whale sharks visit the MCBR waters from May to September and sometimes they can be found even earlier feeding on the spawn of a small tuna fish called “bonito”. This event attracts massive concentrations of these filter-feeders! Ecotourism based on whale sharks has been very important in the region for over a decade representing the main source of income during the year for most local people.

We are happy to report that this season has been very important for the research purposes of the Manta Caribbean Project, because after much preparation we finally crystallized a collaboration with Océanos Vivientes A. C. This has culminated in the deployment of four satellite tags on oceanic mantas and the collection of several biopsy samples! During our two days of work, we were surrounded by whale sharks and manta rays; we estimate that there were close to eighty sharks and fifty manta rays sharing the sea with us, a sight to see!

The Manta Caribbean Project and Océanos Vivientes A. C. teams collaborating on the tagging and biopsy work.

This research will help us understand more about the space utilization and migrations of Caribbean oceanic manta rays and their relation to other oceanic manta ray populations nearby. This is specially exciting considering that the Caribbean manta rays visiting the MCBR could be a subspecies of Mobula birostris or even a new species.

Oceanic manta rays are vulnerable species and are fully protected in Mexican waters since 2019, by the NOM-059-SEMARNAT-2010 under the category Special Protection. Océanos Vivientes A. C. and the Manta Caribbean Project hope to obtain funding for more satellite tags and expand this important research project in the following years. Information gathered from our studies will be used to guide conservation and management measures for these amazing rays.