Discovering the Secrets of the
Giant Manta in Costa Rica

This post is one of a series on projects supported by the New England Aquarium’s Marine Conservation Action Fund (MCAF). Through MCAF, the Aquarium supports researchers, conservationists, and grassroots organizations around the world as they work to address the most challenging problems facing the ocean.

In this piece, MCAF grantee Ilena Zanella, shark and ray scientist and co-founder of Misión Tiburón Costa Rica, shares news of their project to study and protect giant manta rays in Costa Rica. MCAF has helped to support the efforts of Misión Tiburón since 2010 as they have worked to conduct research, advocacy, outreach and education programs centered on shark and ray conservation in Costa Rica.

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By Ilena Zanella, co-founder, Misión Tiburón, Costa Rica

I will never forget my first encounter with a giant manta some 20 years ago, in the Catalinas Islands. At the time, I remember thinking of these creatures as “Noble Giants”. The Catalinas are islands of volcanic origin that are located in front of my community, Playas del Coco Guanacaste, in the North Pacific of Costa Rica. Their rocky reefs host a high diversity of marine species, mainly during the months of upwelling. Between December and April, the northeast trade winds penetrate the North Pacific, pushing the surface waters and producing the plankton blooms due to the upwelling of waters enriched with nutrients. For this reason, during these first months of the year filter feeders such as giant mantas visit the North Pacific coasts of Costa Rica.

Yes, noble giants, I think there is no better name for these creatures, which, despite their great size (they can reach 7 m in width) move gracefully through the ocean … they seem to dance in the water. Their large and deep black eyes look at you, analyze you, and connect with you, they are majestic creatures, who at the same time are defenseless and very vulnerable to human actions.

The inquisitive looks on the mantas reflect their intelligence. Among fish, they have the largest brains in comparison to their body weight, and have proven to be very social with numerous reports of their intra and interspecific interactions. Although they are “giant” animals, little research has been carried out in the world on their natural history and in Costa Rica few efforts have been made in research and conservation of giant mantas. From the reports of divers and fishermen we know part of the places where they congregate, but we do not know about their residence, their migrations and the impact caused by anthropogenic actions. Many secrets still surround them.

Globally, the main threat to the giant manta (Mobula birostris) has been fishing, directed or incidental. The international trade of manta gill plates has increased in response to the demand of the Asian market. This fishing pressure has globally degraded their populations. As a consequence, in recent years a worldwide concern has arisen towards the giant manta: it is currently included in the Red List of the IUCN (International Union for Conservation of Nature) as Threatened, Vulnerable, as well as in Appendix I and II of CMS (Convention on the conservation of Migratory Species), and in Appendix II of CITES (The Convention on International Trade in Endangered Species of Wild Fauna and Flora). In Costa Rica, the giant manta and the other species of the Mobulidae family do not represent a fishery resource, their capture and trade is prohibited under Decree No. 38027-MAG.

Despite this, the inadequate management of critical sites for the giant manta can negatively impact the health of their populations. For example, mismanagement of marine tourism and interaction with fishing gear cause stress and physical damage to individuals visiting these essential habitats, altering their behavior, residence, and possibly their life cycle.

Thanks to the support of the Marine Conservation Action Fund, last year the Misión Tiburón team formally began identifying essential sites for the giant manta in order to promote its conservation. Thanks to MCAF funds, participatory talks and workshops have been held with divers, dive guides, instructors, marine tourism companies, in order to inform about the biology and conservation of the giant manta, its threats and its vulnerabilities, as well as how to develop and promote a protocol of good practices to dive with these creatures, minimizing the stress caused by human presence. Interested people have even been able to help us in the collection of technical information, reporting their sightings through the use of our application “Misión Tiburón”, developed for citizens to identify and report their sightings using a standardized data sheet that includes environmental parameters. This information complements the scientific data collected by Misión Tiburón biologists on the critical habitats identified for the giant manta. Until 2020, more than 300 giant manta sightings were reported in the Pacific of Costa Rica and alliances were established with 30 dive centers throughout the country.

As part of the project, we have also been educating and inspiring children and young people from coastal communities who interact with underwater tourism; through educational activities in schools and festivals to promote ocean conservation and inform specific actions to protect giant manta rays. Children’s enthusiasm and curiosity towards marine life, especially giant animals fill us with energy and hope to continue working and achieve a more conscious and responsible world towards marine life.