Mobulas and Murder: The Hunt for Gill Rakers

All accounts of diving with manta rays detail their majesty and grace, partnered with the sense of awe you feel as their great mass glides through the water so effortlessly above you. It is one of the ambitions of numerous diving fanatics to swim with one in the flesh; however, manta rays – alongside their close cousins, the devil rays – are in trouble. (There is a debate now as to whether manta rays and devils both belong to the Mobula genus, but that is for another blog post, another day). Like much of the marine megafauna enriching our world’s oceans, mantas and devils are under threat, this time from an appalling illegal trade in their gill rakers. I first came across this grotesque trade a few years ago, and still to do this day I cannot wrap my head around the logic behind it.

 

Dharavandhoo Thila - Manata Black Pearl.JPG
Reef manta in the Maldives (Photo by Shiyam ElkCloner)

 

Let me explain. The dried gill plates (known as pengyusai) of manta and devil rays are a sought-after commodity within traditional Chinese medicine and the Asian dried seafood market. Despite only recently being added to traditional Chinese medicine literature, dried gill plates are marketed as curing a range of illnesses, including cancer. There is no scientific literature to back up these claims. China, Sri Lanka and Vietnam are just some of the Asian nations where the trade in gill plates has been documented. However, it is Guangzhou, China that’s the epicentre of where this devastating trade takes place. A 2016 paper in the journal Aquatic Conservation states that “99% of the total estimated market volume of 120.5 tons in 2013” was traded in Guangzhou alone. Although conservation efforts are showing signs of success in reducing the trade of these gill rakers within Guangzhou, there are signs that the trade is relocating to Hong Kong.

Mantas and devils use their gill rakers to filter feed plankton through the water. Like the sharks who are stripped of their highly valuable fins, mantas are illegally fished in vast quantities for their gill rakers – an expensive commodity within Chinese and Southeast Asian markets. Unfortunately, their populations are vulnerable due to their low reproductive rates and high susceptibility to being fished, both intentionally and as bycatch – many migratory paths of these elegant fish are trespassed by fishing boats. In combination with climate change and environmental pollution, illegal fishing has resulted in two manta and three mobula species being enlisted on the IUCN Red List. At the moment, the story looks pretty bleak for these graceful beings, but all is not lost.
So, what can you do? Well, supporting an NGO like the Manta Trust is a good place to start. Not only are these majestic fish threatened by illegal fisheries spurred by the illegal trade in gill rakers, but as previously mentioned, climate change, pollution and development also threatened their habitat. And not just mantas and devils, the health of our oceans as a whole is threatened by global threats like climate change, making it paramount that we elicit change now. If making a direct donation isn’t something you’re able to do, maybe try the Give as You Live Initiative. This is great. Every time you shop online, a donation is made to The Manta Trust without costing you a penny. Heck, there’s no excuses why you can’t do this one!

Another great initiative is the Marine Megafauna Foundation. I first came across this wonderful organisation and Dr. Andrea Marshall – a wonderful marine scientist who was the first person in the world to complete a PhD on manta rays! – a few years ago. Of course, donations are also invaluable to the fantastic work this organisation carries out, but you can also help via raising awareness or maybe you fancy a sponsored swim? Whatever you do, everything helps.

Not only are these rays beautiful creatures, but recent research also indicates that they might be self-aware. Fish are more sentient than many of us give them credit for, but this study for me was particularly exciting for future animal behaviour and intelligence studies. With the largest brain of all fish species, this is hardly a surprise – if there is a correlation between brain size and intelligence, but the jury is still out on that one. Stronger protective legislation and policy is without doubt required to secure the future of these magnificent rays, but there are things we can do now. Education and outreach are fundamental to conservation and this is no exception. And for that, we can all play a role.

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