When one thinks of manta and mobula ray research and conservation you might picture diving in crystal clear tropical waters while counting elegant rays flying overhead. In reality though it’s often much less of a dream job than one would think.

On a typical morning in the life of Daniel Fernando from the Manta Trust, the alarm rings at 4am, which means it’s time to visit the local fish markets. Daniel has mainly worked on the mobulid fishery trade in his native Sri Lanka, roaming the markets to collect data and better understand what drives these kinds of fisheries.

This data will hopefully lead to better conservation measures of these majestic animals and give us more insight into the lives of one of the most charismatic and captivating marine species.

A gory prize - the freshly butchered gill rakers


Mantas and devil rays (Mobula) belong to the Mobulidae family, which contains nine species of Mobula rays and two species of manta rays. Mobulids can be found in tropical water around the world.

As divers we all dream of encounters with these beautiful animals and if we do have the privilege of diving with them they will often be amongst the most memorable dives we’ll ever do. Their charisma and beauty also make them a flagship species for wildlife conservation. Who doesn’t love a giant fish that appears like it can fly underwater and occasionally leaps out of the water as well?

They’re also known to have the largest brain-to-body mass of any fish and some scientists even believe they can recognise themselves in a mirror. On top of all this they are an ecosystem indicator, and studies also suggest they play an important role in the food chain, decomposing on the bottom just like whales and whale sharks do. This phenomenon is called food fall and provides food for bottom dwelling species. Some studies suggest they can bring nutrients up from the bottom and transfer carbon from the surface to the deep sea. Unfortunately for these intelligent elasmobranchs they are overfished in many parts of the world, which is causing great stress on the health of their population.


According to the IUCN Redlist, out of all mobulids, four species are near threatened, three are vulnerable, one is endangered and three are data deficient (meaning we don’t know enough about them to determine how the population is doing). Mobulas and mantas are extremely vulnerable to overfishing as they mature late and have a low reproduction rate. Mantas might only have one pup every three to six years and only start reproducing when they are eight to 10 years old. While they are long-lived at 40 years, they still can’t handle much fishing pressure at all and it’s hard to believe any kind of fishery targeting these species can be sustainable.

A gory prize – the dried gill rakers

The main threat they face nowadays is caused by the demand for their gill plates, which are dried and then used as a pseudo-medicinal health tonic in China called ‘Peng Yu Sai’. Some believe it can cure many ailments, ranging from bad skin to respiratory problems, but none of this is based on scientific research; in fact it is proven that these gill plates contain toxins like arsenic, cadmium, mercury and lead. This hasn’t stopped the gill plate trade from severely threatening mobulid survival. Another interesting fact is that mobulid gill plates are not officially recognised as Traditional Chinese Medicine (TCM) by most TCM practitioners nor are they listed in any standard TCM medical guides.

In Sri Lanka, where Daniel Fernando focuses his research it’s no different, the gill plates are the most valuable part of any dead mobulid and are dried and sold for “medicine”. The meat is often sold at a cheap price and consumed locally. In Sri Lanka manta and mobulas are not targeted but rather kept by fishermen as “non-discarded” or “targeted by-catch” since they can make a lot of money out of the gill plates. The fishermen who often catch and sell mobulid rays mainly go out for tuna; it’s the fishing method they use, such as purse seine nets, that catches a lot of mobulids. The worldwide demand for tuna definitely has an impact on these charismatic animals.


Sri Lanka has no tourism directly associated with mantas and mobulas at the moment. The tuna fishermen go out for days, and even weeks, on end and mostly catch these rays far offshore, making manta and mobula tourism not a very likely alternative to fishing.

Creating alternative livelihoods for fishers is the only way to curtail this destructive fishery, something Daniel hopes his work will achieve

Tourism related to wildlife encounters is on the rise in Sri Lanka and hopefully this will trickle down to more protection of species like mantas and mobulas. The data Daniel Fernando collects at the markets is essential in proving this is not a sustainable fishery and won’t last long. Currently Daniel’s research estimates that there are between 600-1,000 mantas and 20,000 to 50,000 mobulas landed every year in Sri Lanka alone, which can never be sustainable.

Globally there have been some success stories. In 2013 at the CITES (Convention on International Trade of Endangered Species), mantas were listed in Appendix II, meaning the export or re-export can’t be carried out without a permit within countries participating in CITES. In the Philippines, mantas have been protected since 1998 and Indonesia recently declared the world’s largest manta sanctuary by banning fishing for them within the country’s exclusive economic zone.

It’s easy to see why countries that benefit from manta ray tourism would protect the species. According to a 2014 report by Wildaid the estimated annual global tourism value of manta and mobula rays is US$140 million while the dried gill plate trade would be less then 25 percent of that. The tourism value of a single manta during its lifetime can be US$1 million while at a market they are sold for US$40 to 500.

For the rest of this article (Scuba Diver 2015 Issue 5 No 83) and other stories, check out our past issues here or download a digital copy here.

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