Study Reveals World-Record Deep Dives for Reef Manta Rays

March 18, 2020

Deep Offshore Coastal Waters With Significant Fisheries Near Known Manta Ray Populations Should Be Included in Marine Protected Areas

Captured via drone: A reef manta cruises along the surface.

Noumea, New Caledonia (March 18, 2020) – The first data collected on the diving behavior of reef manta rays (Mobula alfredi) in New Caledonia has considerably extended the known depth range for this vulnerable species in global decline.

The study, published today in the journal PLOS One and a collaboration between the University of New Caledonia, Aquarium des Lagons, Manta Trust, and Conservation International, used pop-off archival satellite tags to track the diving behavior of nine reef manta rays in the waters of New Caledonia. All nine of the tagged mantas recorded dives regularly exceeding 300 metres, while six of them dived below 450m — exceeding the deepest previously recorded dive of 432m by a reef manta in the Red Sea. The deepest dives recorded in the study were by a 2.4m wingspan female reaching 624m, and a 3m wingspan male that shattered the previous “world record” by over 200m with a maximum depth of 672 metres.

Manta rays are listed as vulnerable on the International Union for Conservation of Nature Red List. While the New Caledonian population seems healthy, in some countries, declines of up to 80% have been recorded, especially because of targeted hunting and unintentional fishing. This new information provides insights vital to their conservation, particularly those populations recorded near open ocean areas with significant fisheries activities.

“Marine protected areas designed to protect manta rays typically focus on coastal and reef areas, and rarely extend into deeper offshore waters. This research shows that reef mantas regularly utilize these deeper waters, where we already know other ocean voyaging species such as whales, sharks and turtles are also present. To ensure we do not lose these emblematic species, this broader habitat needs to be included in Ocean conservation efforts,” said François Tron, Country Director of Conservation International’s New Caledonia program.

“Manta rays have very strong value to Pacific islanders, including to some Kanak, the indigenous peoples of New Caledonia. They are a powerful emblematic animal for raising environmental awareness and that they also provide great value to the tourism industry and to local Kanak communities if managed sustainably,” said lead author Hugo Lassauce ISEA, University of New Caledonia.

“In New Caledonia, manta rays don’t seem significantly threatened; however land-based erosion may affect their reef habitat quality and their gills as filtering animals; disturbance from tourism may also affect them. Therefore, the identification of and sustainable management of key manta aggregation sites is important to ensure we can monitor their population health, particularly as land degradation continues and targeted tourism increases around these animals,” said François Tron, Country Director of Conservation International’s New Caledonia program.

“New Caledonia’s manta ray population is unexploited and so provides us with an opportunity to understand these animals in the absence of the hunting and other pressures these animals face elsewhere. This potentially provides us with knowledge that could help restore other populations globally, especially where hunting and negative fisheries interactions are still common,” said lead author Hugo Lassauce, ISEA, University of New Caledonia.

Conservation International is working to increase knowledge of manta rays globally and are involved in research efforts in New Caledonia, Indonesia and New Zealand to better understand their movements and conservation needs.

Mark Erdmann, Conservation International’s Vice President of Asia-Pacific Marine Programs and a co-author on the study, said: “We’re delighted with the results of this important study in New Caledonia, and we’re now using the very same satellite tagging technology on manta rays here in New Zealand. To do this, Conservation International is partnering with the New Zealand Department of Conservation, the Tindale Marine Research Charitable Trust and Manta Watch New Zealand to investigate the movements and diving behaviour of the oceanic mantas frequently encountered offshore by New Zealand recreational fishers. In 2019 we successfully deployed two satellite tags on mantas off Northland, and we aim to deploy five more tags before winter. We have some very exciting data from the 2019 tagging effort, but are waiting for results from a few more tags before publishing our findings."

For media use:

For more information, contact: Emmeline Johansen, Communications Director, Asia Pacific Field Division, Conservation International | Mobile +64 277 793 401 | Email

About Conservation International

Conservation International works to protect the critical benefits that nature provides to people. Through science, partnerships and fieldwork, Conservation International is driving innovation and investments in nature-based solutions to the climate crisis, supporting protections for critical habitats, and fostering economic development that is grounded in the conservation of nature. We work in 30 countries around the world, empowering societies at all levels to create a cleaner, healthier and more sustainable planet. Follow Conservation International’s work on Conservation News, Facebook, Twitter, Instagram and YouTube.


About Aquarium des lagons, Nouvelle-Calédonie

The “Aquarium des Lagons” is a public organization operated jointly by the Government of New Caledonia, the Southern Province and the City of Noumea. It aims to display to the public the aquatic ecosystems of New Caledonia, to raise public awareness to environmental issues and to carry out scientific research on marine and freshwater ecology. More information on,,,,