Most of our posts recently have been manta ray info and travel adventures; fascinating but it’s probably time for a project update!
We arrived at the tail end of the rainy season here in Bora Bora…a tail that ended up being longer than we thought…in fact it’s still going. I mentioned before that when it rains heavily the manta dive site gets pretty washed out with silt making the visibility quite poor. This week though we have been able to get there more regularly and got some dives in which has been great. We have seen a manta or two and we’re persevering despite the milky water and hope that it will clear up soon! Obviously the clearer the water the easier it is to see mantas and identify them. Hopefully as the water clarity improves the number of dives will continue to go up as will the number of manta photos we have to share with you.
Oh and it’s a 20 mile round trip on our newly purchased bikes in 30°C heat to the manta dive site, so we’ll be fitter than ever in no time. The things we do for science!
On to cleaning stations! A few weeks ago I said I’d talk a bit more about them, what they were and why animals like manta rays use them. Well, that day has come! Cleaning stations are areas of the ocean, usually part of coral reefs, where large marine animals like mantas but also sharks, turtles, other species of ray and large fish come for a good clean up. When they arrive they sit almost stationary in the water and usually open their mouths or behave in some other way to indicate that they would like to be cleaned. At this point a little task force of specialist shrimps and fish (mostly wrasse and gobies) descend and eat any parasites, dead skin, bacteria and mucus off of the body surface and gills of the larger fish, even going inside the mouths of sharks to clean.
This process is called mutualistic symbiosis. A fancy way of saying that both parties (the manta ray and the cleaner team) get something out of the experience. Cleaning helps keep the mantas healthy as they stay parasite free and any dead or infected skin gets removed from wounds which helps them to heal faster and prevents infection. At the same time the cleaner team are provided with a regular and easy dinner. Manta rays are known to spend hours each day at cleaning stations and return again and again to the same ones; not only day after day but also year after year. This makes them really useful places to study manta ray populations and health.
As the cleaning stations are fixed locations they are also popular places for snorkel and dive operators to take guests to see these amazing animals. It is really important that codes of conduct are adhered to by everyone at these stations so that the natural behaviours of the mantas are not altered. If you’re lucky enough to be going on holiday to somewhere where you might get to see these animals, please take a look at the Manta Trust’s guide for ‘Swimming with Mantas’ before you leave.
Cleaner fish are very eager to clean any animal that seems in need, as I found out on a dive yesterday. We were doing our safety stop (which is just hanging in the water for 3 minutes at 5 meters at the end of the dive to let any excess nitrogen slowly leave our bodies) and a cheeky little cleaner wrasse swam over. It started nibbling on my legs and giving me a good old clean! I don’t think I have much in the way of parasites on my legs but maybe a little bit of peely sunburn – enough for a snack for a cleaner fish anyway. Check out the little video that Bex shot below.
All for now, thanks for coming by and reading.
Being a magnificent, ethereal ocean giant that traverses the deep and mysterious blue like a BOSS does not, alas, protect you from the reaches of industry and human impact on the environment. Far from it! Along with countless other marine species, manta ray populations around the world are now fighting for survival against man-made pressures including fishing, habitat loss, pollution and climate change and both Oceanic and Reef manta species are listed as Vulnerable by the IUCN.
One particularly worrying and relatively new threat to these colossal, briny beasts is that of the gill plate trade. I have mentioned in a previous post that manta rays have specialised gills which they use to filter feed. Inside each of a manta’s ten gill slits is a set of feather-like gill plates (a circle of thin cartilage filaments) which trap planktonic food as water passes through a manta’s mouth and out of through the gills. Manta and mobula rays are now being hunted specifically for their gill plates which are extremely valuable for their use in Traditional Chinese Medicine.
Gill plates are dried and usually eaten in a soup (see image below). The soup may not look all that appetising to our Western tastes (yup, it's garnished with pipefish) but retailers promote that consumption of the plates can treat all manner of health issues ranging from asthma to chicken pox to cancer and that their filtering properties help to boost the immune system and detoxify the blood... all of which helps to explain why so many people are slurping down this 'wonder-drug', pipefish and all! However there is of course no scientific evidence to back up any of these claims, as is the case for so many of these Traditional Medicines made from desperately endangered and ill-treated animals.
What makes this story all the more frustrating is that research into traditional literature has revealed no mention of gill plates. It seems they are not actually a true Traditional Medicine but a remedy invented in recent years by Chinese retailers seeing an opportunity to market new products as 'revived' ancient medicines, playing on the fears of consumers over disease outbreaks such as Bird Flu and SARS. The result: big new manta and mobula rays fisheries popping up in India, Sri Lanka and Indonesia.
That alone sounds like enough for a big, flappy, cartilaginous fish to have to deal with but sadly there is more to tell. Further posts to follow soon on other threats to mantas and what you can do to help protect them. You can read more about the gill plate trade on the Manta Trust's website.
Thanks for reading!
Two things to cover in this post! First up, we finally got to visit the dive site called Anau; frequent home of the Bora Bora manta rays - exciting! Secondly the fantastic Cécile Berthe who is working as our Project Manager and overseeing/helping us out from her position at the Insular Research Center and Observatory of the Environment (also known as CRIOBE) has agreed to write a guest post.
On to anau
Now as fun as it would be to just dive every day for the next 6 months (and believe me we considered it) we’ve been on a self-imposed diving ban the last few days so we could work on some project bits. The agreed exception was if there was a trip to Anau on the cards and this morning we got the call that we were on! Anau is round on the East side of the island and close to the coast. It’s so close to shore in fact that if there is heavy rain all the soil and silt that runs off from the mountain turns the water to soup. Diving in that kind of water is not only rather difficult but also you can’t see your hand in front of your face let alone a manta ray! The reason it’s so popular with mantas is that it’s highly productive…this means full of delicious plankton, a manta’s favourite food. It didn’t disappoint and we were treated to three reef mantas ranging from a small one at around 1.5m to a large female at 2.5-3m. So awesome, great to know they are around and what a start to our manta diving!
Above photo by Bex of one of the mantas we saw today…all the planktonic food in the water makes it great for manta rays but not so great for taking photos.
Hello from Cécile
Hopefully this is the first of what will become a regular feature of this blog. We’d like to introduce you to some of the manta-friendly people we meet along our way. Folks that have helped us out with the project, with diving, with manta info etc. and Cécile is a great starting point. She is always on hand for any questions we have and has led this project and directed us since we’ve been in French Polynesia. Over to you Cécile…
“My name is Cécile. I’ve lived in French Polynesia for 5 years and work at the Insular Research Center and Observatory of the Environment as communication assistant. I’ve dived since highschool. But as I am from the North of France, I used to dive in lakes or in the sea where you barely see your hand…I dreamed about coral reef ecosystems through aquariums I visited that showed me all the beauty the underwater world has to offer.
One day I had the chance to fly to the Pacific islands. My first Manta encounter happened in New Caledonia. She was alone and we were three divers amazed by this huge female flying in front of us. Since then I’ve had more chances to spend many more times with Manta rays in French Polynesia, where they seem to have a peaceful place to live. Here they are not chased, just observed by passionate people.
I decided to join a local organization, the Observatoire des requins et des raies de Polynésie (ORP), that works to increase knowledge about these animals and encourage sustainable behaviours around them so that humans and sharks/rays can live together for a long time.”
Thank you Cécile and thanks for all your help so far.
Until next time,
Never underestimate a grey day. Magical things can, and often do, happen on the most overcast and uninspiring of days. Scuba divers know this well, as do us Brits.
Early this morning we scampered down to Topdive’s Vaitape site excited for a dive or two to test out some of our new equipment and to get our fins wet for the first time since arriving. A fortnight of rather biblical, tropical thunderstorms has meant a dry week for us (by which I mean no diving, we still got very wet!) so we were absolutely desperate to get into the ocean.
After loading up the boat our wetsuits were already soaked through with rain and our hair stylishly plastered to our faces. We set out on a choppy sea, heading away from the island to find clearer water. Upon arriving at our site and starting to set up our equipment I soon felt an unmistakable hint of sea sickness. A non-scuba diver might well look at this group of loonies, bobbing about in a small boat on a choppy sea, windswept and soaked to the bone, readying to jump into the uninviting steely void heaving beneath them and question what on earth they were doing; and at this point in time, with my stomach churning, I have to admit I was questioning it myself a little too. Staggering to the back of the boat, green around the gills, graceful as a drunk seagull, I stepped out of the grey, drizzly day and into the blue.
As soon as you descend into the ocean on a day like this two things happen, your sea sickness vanishes and so does the miserable weather. The underwater world, though a little less bright than usual, is still a gorgeous and inviting place to be; it is almost a shock to arrive back at the surface and be greeted by such a colourless scene an hour later. During our two dives we were treated to multiple Blacktips, my first Lemon Shark, courting (successfully from what we could see!) Spotted Eagle Rays and a big chunky Barracuda as well as beautiful corals, fish, crustaceans and lots more.
Most excitingly of all between our two dives we spotted our first manta ray here in French Polynesia and Graham and I were allowed to jump in briefly in to take a closer look. A small (by manta standards) ray at around 2m wide, the Y-shaped markings on its back told us it was a Reef Manta. Project on!
We returned to shore feeling thoroughly satisfied, sea sickness long forgotten, and were greeting by the first glimpse of sunshine in the sky that we’ve seen all week.
Thanks for reading.
So as promised, let's get some clarity on what a mobula ray is shall we? The Mobulids are a family of rays that contain the two species of Manta Ray and nine species of Mobula Ray. So most simply mantas and mobulas are cousins. I mean phylogenetically of course, not in a first cousin Claire that we only see once a year at Christmas kind of a way. Manta and Mobula are the names of the two genus’ in the family Mobulidae and they are very similar to each other indeed. The main differentiating feature is their size with adult mantas generally much larger but the shape of their mouths and their cephalic (that’s a fancy word for head) fins differs between the genus’ too.
The photo above shows just one of the nine Mobula Ray species (which are commonly known as Devil Rays hence the hilarious title of this post) and like mantas, they too are beautiful animals.
As nice as mobulas are (and we hope to see a few of them whilst we are out here!) the two species of manta ray are the reason we’re in Bora Bora. One is called the Reef Manta (Manta alfredi) and the other the Oceanic Manta (Manta birostris). As Bex mentioned last time out they are both magnificent beasts and a large Oceanic Manta can get to over 7m across! They’re quite tricky to tell apart as although the Oceanics get much larger it is of course possible to encounter juvenile and sub adults which confuses things slightly. The easiest way is to look at them from above and see what shape the black markings on their heads are. The Oceanic Manta has a T-shaped shoulder stripe and the Reef Manta has a Y-shaped marking in a similar position. For more info on how to tell them apart visit the Spot the Difference page on the Manta Trust website.
The photos below show a Reef Manta (left hand side with Y-shaped black patch) and an Oceanic Manta (right hand side with T-shaped black patch) next to each other. Hopefully you can see the difference in their patterns?
The two species have quite different habits with the Reef Manta (as the name suggests) associating with small groups of islands or reefs in shallow waters. They tend to be highly social sticking to a specific home range whilst following seasonal changes in food availability. We call this a resident species and it is sometimes known as the Resident Reef Manta. The Oceanic Manta is in contrast a more open water species spending the majority of its time feeding out in the big blue! It comes in to reefs to visit cleaning stations or at particular times of year for plentiful feeding. (By the way, a cleaning station is like an underwater carwash for rays, fish, sharks, turtles etc. where they get little parasites or dead skin removed by a crew of specialised cleaner shrimp and fish. These are awesome and I’m sure we’ll post more on this later!). It is during these times, when the oceanics are more coastal, that if we are lucky enough we get a chance to dive with them.
There are very few places in the world where one can hope to see both species in one place and French Polynesia is one of those places. Whether we do see both species together and, if we do, how they interact with each other is one of the reasons we are here. Studying this is just one exciting aspect of the research we hope to carry out through observing them over the next 6 months. More details on our project and what we hope to achieve in the coming posts.
Thanks for reading!
Hello, welcome and thank you for visiting our mobula blogula! I am Bex, I work at the SEA LIFE London Aquarium but along with my partner Graham (also of the London Aquarium) have taken a sabbatical and moved to Bora Bora, French Polynesia, to work for the Manta Trust. We would really love to share some of our experiences and learnings with you over what we hope will be a really exciting, productive and manta-filled 6 months.
It is only our second day on the island of Bora Bora and we are currently sitting on a veranda gazing out over an overcast but still stunning view of the ocean and island volcano, nervously listening to the sound of rain hitting the corrugated and not entirely waterproof roof that we hope will keep our laptops safe and dry. It truly is a wonderful part of the world to be in (though it looks unnervingly like the island from Jurassic Park) but we are not here for the views or the tropical climate. We’re here for the manta rays!
So what is a manta ray you might well ask? Manta rays are some of nature’s gentle giants; they reach enormous proportions yet feed only on tiny fish and zooplankton. The largest mantas can reach over 7m from wing-tip to wing-tip and weigh in at about 2 tonnes. Just stop and think about that for a moment. A single, large manta ray probably covers more m² than the average London flat and weighs as much as a rhino. They. Are. BIG.
Gliding through the ocean, driven by their epic, beating pectoral fins, swooping and rolling like acrobats to filter plankton from the water with their specialised gills, mantas are effortlessly graceful and mesmerising to behold. They have the largest brain to body ratio of any fish and are believed to be intelligent, sociable beings with distinct personalities. Some individuals are known to seek out interaction with humans, seeming to enjoy the feeling of diver’s bubbles tickling their bellies.
Manta's are everything you could want in a sea creature; big, beautiful and mysterious. Scientists have only been studying mantas properly for around a decade so there is still a lot to learn! Making the Manta Trust's work and our time here in Bora Bora all the more important and exciting.
Now it is getting dark and my tummy is rumbling so the time has come to wrap this up, evict the tiny gecko that is using my laptop case as cover to ambush delicious ants and head back inside. Thank you for reading! More posts to follow soon.
P.S. You might well be wondering why we've called this blog the 'mobula blogula' and what a mobula is? All will be revealed in the next post!