The waters just off the northwest coast of Madagascar have been determined as an important habitat for both manta and devil rays; a surprise finding that reignited calls among scientists behind a first-of-its-kind research effort on mobulids within this specific region, for increased protections for these endangered species. 

A new study – published this month in Environmental Biology of Fishes – documented no fewer than 255 encounters with three mobula species between the years 2016 and 2022. Among them, spinetail devil rays (Mobula mobular) were the most commonly recorded with 165 sightings; followed by oceanic manta rays (Mobula birostris) with 60 and the shorthorned pygmy devil ray (Mobula kuhlii) with 30.

These are important findings, the team has suggested, highlighting not only the encouraging signs for all three species previously categories as ‘endangered’ by the IUCN Red List, but for the wealth of information it provides scientists reading between the lines. It’s important to note, for instance, the numbers of species that weren’t recorded during the study.

Concerns have since been raised that reef manta rays (Mobula alfredi) may be in decline in the area – an area northwest of the country called Ampasindava Bay – as well as three other species of mobulids. Reef manta rays had previously been identified in the area, but there have been no confirmed records of them since 2015, suggesting that populations could be in decline locally.

“It’s worrying that we haven’t recorded any reef mantas since 2015,” said lead author, Stella Diamant, founder of the Madagascar Whale Shark Project. “Yet, we have identified three other mobulid species, including oceanic manta rays.

“These amazing animals are listed as endangered, facing a very high risk of extinction, and face many threats including targeted fisheries, bycatch, and boat strikes. This study highlights how important it is to protect the species from further decline.”

This study was based on sighting data in the Ampasindava Bay area, collected during opportunistic tourism encounters as well as citizen science submissions, tourism operator reports, and social media records.

Oceanic manta rays, shorthorned pygmy devil rays, and spinetail devil rays were frequently observed and were regularly seen feeding and foraging. Oceanic manta rays and shorthorned pygmy devil rays were encountered in almost every survey year with courtship behaviours also observed for these species.

Ampisindava Bay is made up of the islands of Nosy Be, Nosy Sakatia, Nosy Komba, and the Ampasindava Peninsula on mainland Madagascar. These waters are well-known for the occurrence of large planktivores, such as whale sharks (Rhincodon typus) and Omura’s whales (Balaenoptera omurai). This study now confirms that these waters provide a significant habitat for mobulid rays, which are commonly sighted in the region.

“We already knew that Nosy Be is a global hotspot for whale sharks, which are also endangered worldwide. This new study shows the region is also a haven for other threatened plankton-feeders,” said Dr Simon Pierce, a co-author and executive director of the Marine Megafauna Foundation.

“More work is needed to protect these giant rays from harm – especially from indiscriminate gillnet fishing.”

Mobulids are caught regularly in nearby fisheries and experts are concerned by the potential impact of fishing on threatened sharks and rays. Bottom-set gillnets – fishing nets anchored to the seabed to catch fish that swim into them – are being used increasingly in the Nosy Be region and pose a direct threat to mobulids and other threatened species.

Marine Protected Areas (MPAs), such as the existing Ankarea and Ankivonjy MPAs, and the proposed Tandavandriva corridor MPA that link them together, could well provide the spatial refuge for threatened species like mobulids. Only, however, if they are well enforced with the appropriate management measures for such species, the Manta Trust has argued.

Meanwhile, a lot of protection could be derived from Madagascar’s growing position as a destination for eco-tourists. In fact, many communities across Madagascar are, today, reliant on eco-tourism for their livelihoods.

“Marine tourism is estimated to bring in over one million dollars to the local economy each year, so protecting these enigmatic species is vital for Malagasy communities as well as the environment,” said the study’s lead author, Stella Diamant.

This is the second study to emerge on the habitual migratory behaviour of mobulid species this month. New research tracking the journey of endangered spinetail devil rays across the Mediterranean Sea has this week confirmed their regular movements between productive western and central Mediterranean areas in the summer and eastern Levantine waters in the late winter and spring.

Using satellite telemetry, this study tracked nine rays between 2016 and 2022 to better understand their seasonal movements. It found that these marine animals were not adverse to some long-distance travel with one of the rays tagged off Gaza swimming to Spain and back to the Levantine Sea in just one year.

Equally threatened by overfishing as their counterparts in other areas, these rays are particularly vulnerable to fishing practices in the winter months, when they form large groups, making them a target for significant harvests.

This study – titled Insights into spinetail devil ray spatial ecology in the Mediterranean Sea through satellite telemetry, published in the scientific journal, Nature –  provides critical insight into understanding migratory patterns, which – in turn – is vital for developing the most effective means of protecting the species. It recognises that place-based conservation efforts are urgently needed, especially in areas of high fishing pressure.

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