Madagascar · Global Manta Ray Program · Since 2016

Madagascar Manta and Devil Rays

Seven years of surveys off Nosy Be documented three threatened species of manta and devil rays feeding in the same bay, but no confirmed records of reef manta rays since 2015.

Led by Madagascar Whale Shark Project, with MMF

255encounters with manta and devil rays, 2016 to 2022

3threatened species feeding in the same bay

13oceanic manta rays with injuries from fishing gear or boats

Up to 30rays caught by a bottom-set gillnet in a single night

The waters off Nosy Be are known for whale sharks and Omura’s whales. The first dedicated study of manta and devil rays in Madagascar, led by the Madagascar Whale Shark Project, found three threatened species feeding in the same bay, and no confirmed records of reef manta rays since 2015.

Manta and devil rays are among the most threatened of all vertebrate groups, mainly as a result of overfishing, and every species in this study is listed as Endangered or Vulnerable on the IUCN Red List. Between 2016 and 2022, Madagascar Whale Shark Project researchers and volunteers recorded the rays they encountered from marine tourism vessels off Nosy Be, in northwest Madagascar, and compiled further records from tourism operators, citizen scientists, and social media. Stella Diamant, who founded the Madagascar Whale Shark Project in 2016, led the study.

What the project has done

Published the first dedicated study of manta and devil rays in Madagascar (Diamant et al. 2025), documenting 255 encounters with three species.
Identified a possible local decline of reef manta rays: none have been confirmed in the area since 2015.
Documented the fisheries that catch these rays, including bottom-set gillnets that can catch up to 30 rays in a single night.

An Omura's whale off Nosy Be, Madagascar

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Study findings

Three species in one bay

The most common species was the spinetail devil ray (Mobula mobular), with 165 encounters, followed by the oceanic manta ray (M. birostris, 60) and the shortfin devil ray (M. kuhlii, 30). Encounters peaked in October and November, the same months as the whale shark season.

All three species fed on dense patches of zooplankton in Ampasindava Bay, sometimes alongside Omura’s whales and whale sharks. Spinetail devil rays were observed in courtship trains, in which several rays follow a female, in about 10% of encounters toward the end of the season in December. One adult female oceanic manta ray was photographed in four separate years between 2016 and 2022.

Spinetail devil rays off Nosy Be, Madagascar

Decline in reef manta ray sightings

Reef manta rays (Mobula alfredi) once visited a cleaning station (a reef site where small fishes remove parasites from mantas) known to dive operators as Manta Point. However, sightings became rare after 2007, and none have been confirmed there since 2015. Without long-term catch records the cause cannot be confirmed, although reef manta rays are known to be highly vulnerable to small-scale fisheries.

An island and its fringing reef in northwest Madagascar, from the air

Threats

Rays are caught in bottom-set gillnets off Nosy Be and nearby Nosy Faly, and as bycatch in nets set for tuna and billfish. The meat is eaten locally, sold dried in markets, and transported to markets in northeast Madagascar, likely for export. However, gill plates, the filtering structures whose trade drives fisheries for these rays elsewhere, were neither exported nor sold in local markets.

Scars from fishing gear and boat propellers were common, with 13 oceanic manta rays carrying injuries from human causes. Tourism boats also sometimes crowd the rays, as they do whale sharks.

Study recommendations

Extend Madagascar’s marine tourism code of conduct, which since 2024 has covered whale sharks, sea turtles, and cetaceans, to manta and devil rays.
Monitor fisheries landings around Nosy Be, and introduce management measures that reduce ray deaths in gillnets.
Align national fisheries law with Madagascar’s commitments under the Convention on Migratory Species, which lists all manta and devil rays on Appendix I.
Ensure the planned marine protected area linking Ankivonjy and Ankarea covers the rays’ feeding area, since most of the feeding, cleaning, and courtship the team observed took place outside the current protected area.

Nosy Be has also been recognized as an Important Shark and Ray Area, a site identified as critical habitat for sharks and rays, partly because of these rays.