In the Field – Monitoring Sharks and Manta Rays on a Remote Island (PART 1: Manta Rays)
SHOW NOTES
Our adventure begins with a 250km flight from the main island of the Seychelles, Mahé, to D’Arros, a tiny dot of an island in the middle of the Indian Ocean [2.30]. We are headed to meet the team of the Save Our Seas Foundation D’Arros Research Centre (SOSF-DRC), whom we will be spending the week shadowing as they conduct their research and monitoring of the island’s vast diversity of wildlife.
We first meet research officers Dillys Pouponeau and Ellie Moulinie, who were born and raised in Seychelles [3.45]. For them, D’Arros is something special. “It’s an island that has set aside purely for conservation and the conservation work, the work that we’re here for, comes as priority,” says Dillys. “And I guess this makes it a real dream for every scientist, every biologist who would want to come and work here,” Ellie agrees. “D’Arros Island to me is paradise. It’s pristine. It’s a safe haven for a large amount of biodiversity from land animals, birds, tortoises, sea turtles, marine animals, sharks, manta rays, animals you won’t see on or around inhabited islands, like the inner islands of Seychelles.”
This wildness is evident as soon as you touch down on the island’s tiny airstrip [6.25]. The first thing that hits you is the sounds of the forest: the buzzing of insectivorous life, and the chattering of the fairy terns that cluster in the trees. Then, on the short trip to the research centre, the gentle rush of waves on the sand starts to grow louder.
The D’Arros Research Centre is located right on the water’s edge, overlooking the ocean where reef manta rays come to feed every day. Here, we are met by Research Director for the SOSF-DRC, Dr Rob Bullock, and Programme Director Henriette Grimmel [9.17]. They provide some background to the island, explaining its geography and history. “These are all the Coraline Islands, built by the sea of old reefs from sand, etc,” explains Henriette. “And you have D’Arros and then very close to it, the atoll called St Joseph. They’re divided by a 1 kilometer channel.” Where D’Arros is round and surrounded by reef, St Joseph is shaped more like a finger, fringed by reef with a sheltered lagoon in its centre. D’Arros and St Joseph have a vast diversity of habitats, which in turn, support a huge variety of marine life. “So the marine life around D’Arros is phenomenal, and unlike anything I’d ever experienced before. From the shoreline to the reef crest, to the drop-off, to the seagrass flats, to the deep waters, there’s just this huge abundance and variety of life that calls this place home. From you know, the obvious stuff – the corals, the reef fishes, the sea grasses, the sharks, the rays, the turtles, all the clear and evident stuff. And then the more time you spend here, the more you come to know all of the interesting and cryptic things,” explains Rob.
The reason why wildlife has been able to thrive in these waters is largely down to the ownership of the island [14.03]. Previously, it was a coconut plantation, but when the value of coconut copra began to fall in the 1970s, the Seychelles government put D’Arros up for sale. It passed hands a few times, before the founder of the Save Our Seas Foundation took over ownership in 2012. Previous owners had already established a research centre – mainly focussed on forest restoration, with some coral and turtle work – which came under the stewardship of the Save Our Seas Foundation. Since then, their marine research and monitoring programmes have expanded substantially, which we’ll get a taste of over the next week…
The morning after arriving on the island, we head out on the water to meet one of the ocean’s most charismatic inhabitants: reef manta rays [16.00]. They are a member of the mobulid family, and one of the largest rays in the world, with a wingspan of up to 4 metres. They are also one of the most intelligent fish species, famed for their curiosity and gentle nature. D’Arros appears to be an important place for them, and Dillys’ research is trying to understand why: “Here around D’Arros we have the reef manta rays that feed around the island daily, and year round. In most places these animals are pretty much seasonal, and they are not found in one area for the whole year. They migrate…I think this is what makes D’Arros special is because they’re here year-round despite the season. And this really gives D’Arros such a significance because if they’re staying here it means there’s something special about this place. And this is what we’re really trying to figure out in the research that we do. Why are they here year-round? What are they doing here? How are they using the habitat? So really what is there here that there’s not in other places?”
The team conduct reef manta surveys up to four times a week – our first job of the trip [19.19]. We set out on the boat to where the mantas feed, which is, quite literally, on the DRC’s doorstep. In minutes, we’d found our first mantas. A group of five, who were feeding on plankton at the surface. Our task was to swim alongside them (while maintaining a safe distance) and dive underneath to capture images of their bellies. “The mantas have a unique pattern on the bellies,” explains Dillys. “Each manta has a different pattern, which works similarly [to] our fingerprint. They’re all different and we are able to identify all these individuals that come here.”
In addition to ID-ing the manta rays, we also log information about their behaviour, sex, size, and any injuries or other irregularities that we can see. Dillys also takes the opportunity to take a plankton sample [27.52]. This is part of her individual research project, for which she is trying to understand the conditions that bring the plankton – which the mantas are feeding on – to the surface. As the manta rays rely on aggregations of plankton to feed, Dillys’ research can also give insight into where and when mantas might occur. “I have found that the mantas and the plankton are tidally driven. So they really rely on the tidal movements. And we found that the plankton starts accumulating right before the high tide, peaking right after the high tide, and then drops as the tide drops. And this is where we’re seeing the changes in plankton density and feeding behaviours of mantas,” says Dillys. She has also been able to determine that the abundance of plankton remains consistent throughout the seasons, which explains why mantas occur around D’Arros all year round, something that they don’t do in other places.
Back on dry land, we take Dillys’ samples to the lab to process them [31.25]. The first step is putting the fresh samples in the fridge to preserve them. Next, Dillys removes some samples that have been sitting in the fridge for about a week. She needs to split the sample into two, so that they can be used for two different purposes. She does this using a Folsom splitter – a piece of equipment that looks a bit like a hamster wheel with two separate containers at the bottom. She pours in the sample, turns the wheel, and the sample divides into the two containers. One sample is sieved, then spread out on some foil and placed into a dehydrator for five hours, where it will become a little dried disk of plankton (which Dillys calls “plankton crackers”). From these, Dillys can calculate the biomass of plankton in her sample. The other half of the sample is sieved, mixed with distilled water, and then placed under the microscope. Here, Dillys can identify the different species within her sample. This particular one was full of copepods – a tiny crustacean.
But our work with the reef manta rays was not done for the day. Next up was a scuba dive to Manta Cam, a system installed by the SOSF-DRC to remotely capture photos of mantas at their cleaning stations around the island [40.24]. It’s a short dive from the centre’s doorstep, across a vibrant coral reef filled with reef fishes, hawksbill turtles and blacktip reef sharks, to where Manta Cam sits on the sandy bottom, at about 16 metres beneath the surface. Here, Dillys and Ellie swap over the equipment while a reef manta glides overhead, probably wondering what on earth we’re doing.
The combined footage from the manta survey and Manta Cam are all uploaded to the Seychelles Manta Ray Programme (SMRP), a database of individual reef manta rays from across Seychelles [43.51]. Because of the efforts of SOSF-DRC, along with the data contributed by the SMRP’s collaborators, they have been able to double the number of mantas ID’d, and earlier this year reached a milestone of 500 individual mantas identified in the database – a number that is continuing to climb. This data provides crucial information that can be used towards the conservation of manta rays in Seychelles, and beyond. “The reason it’s important is because it gives us a highly accurate image of the population, because we can identify individuals,” says Henriette. “The more you’re identifying them, the closer you get to the true number of the size of the population. And you can start having an idea of the incomings and outgoings. You can understand if there’s seasonality to where they are, when they are. For instance, are they here most of the time? Are they going a lot between here and other places? And you can start going into even an individual level of understanding these animals, of how the females differ to the males. How are they different if they’re juveniles and young versus when they’re adults and mature and are interested in mating and stuff like that.
So, you can see the shifts across individuals and across life stages as well through simply just taking pictures, which is a different way of mark-recapture than what we do with the juvenile sharks. You’re just not pit tagging them, because you don’t need to. Because you can visually tell who’s who.”
This is part 1 of In the Field: Monitoring Sharks and Manta Rays on a Remote Island. For part 2, where we take part in shark tagging and monitoring, head here.
ABOUT OUR GUESTS
HENRIETTE GRIMMEL
Programme Director, SOSF-DRC
Growing up in Germany and Switzerland, where competitive swimming and rowing meant that she spent a lot of time in and on water, Henriette has always had a strong connection to this element. At university Henriette studied geography and environmental sciences and it took a few more years before she discovered an interest in diving in Lake Zurich and a fascination for sharks. She followed these up with saltwater experiences while volunteering in Mozambique, where she assisted in whale shark research and fish censuses. After further travels and a dive-master internship in Honduras, she went on to complete an Erasmus Mundus Master’s in marine biodiversity and conservation, conducting her field study at the Bimini Biological Field Station in The Bahamas. She gained further experience in marine research while working with the Large Marine Vertebrates Research Institute (LAMAVE) in the Philippines, where she helped to monitor a mobulid fishery and assisted in shark research in Tubbataha Reefs Natural Park.
Although it was diving and sharks that got Henriette into marine science, she has always been interested in the complexities of ocean management and how humans interact with the marine world, so she completed a second Erasmus Mundus Master’s, this time in maritime spatial planning from the universities of Seville, the Azores and Iuav Venice. Sharks and conservation remain close to her heart, but Henriette also has a very strong interest in understanding ocean processes, ecosystem services and how humans use them, and finding a pathway to governing that use in a sustainable manner.
DR ROBERT BULLOCK
Research Director, SOSF-DRC
Rob can trace his love for science and the marine world back to his youth and to Sir David Attenborough, whose words instilled a curiosity that soon grew into a passion for learning about nature. As an adult, Rob pursued this passion, studying marine and freshwater biology at the University of Hull. As he learned more about the marine realm and its inhabitants, he became particularly interested in the importance of species in healthy ecosystems and the need for science-based conservation. Through his education, he discovered the amazing diversity among sharks, the fascinating roles they play in marine systems and the extreme threats they face.
Rob conducted his PhD research at the Bimini Biological Field Station, where he worked as a Principal Investigator and studied the fine-scale behaviour of young lemon sharks using the Bimini Island nursery sites. He then moved on to broaden his skill set as a post-doctoral research associate with the Marine Biodiversity Unit of the International Union for Conservation of Nature (IUCN), assessing extinction risk to marine species. Rob’s career thus far has taken him to the intersection of scientific research and conservation action, and he is driven to deliver science with tangible conservation outcomes.
ELLIE MOULINIE
Research Officer, SOSF-DRC
Born and raised in Seychelles, Ellie loves the island life. She comes from a family of fishermen living next to the ocean, so school holidays meant enjoying the sun and sea every day and, as a strong swimmer, especially snorkelling and diving. Her love of animals, nature and the ocean and her desire to visit all 115 islands in Seychelles influenced her to pursue a Bachelor’s degree in environmental science at the University of Seychelles. Only after learning how to dive did she realise that she wanted to specialise in marine science and fisheries. As an intern for Global Vision International, she learnt about fish and marine invertebrates and their importance, and how to conduct surveys to monitor them. She ventured further into marine research by volunteering with the NGO Green Island Foundation, helping to conduct surveys on islands such as North, Denis and Fregate. In 2018, Ellie joined an Earthwatch team on Curieuse Island, where she participated in its Coral Communities in Seychelles Project.
Always moving her career in conservation forward, Ellie most recently worked with the Seychelles Islands Foundation as a field research officer on Aldabra Atoll, where her tasks consisted of conducting terrestrial surveys on the flora and fauna as well as marine research as part of Aldabra’s annual marine monitoring programme. As a young emerging scientist and conservationist, she believes it is her duty and responsibility to do her part to protect global ecosystems and threatened species against anthropogenic stressors and the effects of climate change that are causing the loss of biodiversity.
DILLYS POUPONEAU
Research Officer, SOSF-DRC
Originally from Praslin Island, home of the largest nut in the world (coco de mer), Dillys had some amazing experiences as a member of environmental clubs during her school years and these taught her the importance of protecting biodiversity. They inspired her to pursue a Bachelor’s degree in environmental science, specialising in tropical biodiversity conservation, at the University of Seychelles.
As a young environmental conservationist with an interest in all living things and habitat types, Dillys has had the privilege of working on numerous terrestrial and marine projects, ranging from scientific research to environmental education and sustainability projects on several islands in Seychelles. She also has a strong interest in well-preserved biodiverse ecosystems, which she enjoys capturing on video and in photographs that enable her to raise awareness and engage people’s interest. She is keen to fill her professional and private life with anything that is fun, artistic, creative, exploratory and adventurous, as long as it is in the wild. Dillys wishes to pursue her studies further and develop the necessary skills required to become a great scientist and nature photographer, and videographer.
Her career began at the Vallée de Mai Nature Reserve, where she worked as a field research assistant before undertaking her academic degree. After finishing at university, she was employed as the sustainability manager at a five-star hotel, and most recently she worked as the assistant conservation officer with the Island Conservation Society. She worked on Silhouette Island (93% national park and surrounding marine park) and at Aride Island Special Reserve and Marine Protected Area, where she coordinated conservation projects and managed a team of eight.
