Tom Bech Letessier

Five years ago, a bunch of lockdown-weary but knowledge-hungry scientists and conservationists gathered online to hatch their next mission: study the whales & dolphins of the Chagos marine reserve. A key question was whether this remote Indian Ocean archipelago was home to the rare Omura’s whale- an elusive baleen species that was first described in 2003 and only recorded live in 2013! Previous acoustic recordings from Chagos suggested it might be around, but solide evidence was still missing. This week, the team woke up to exciting news- we have confirmed sighting of Omura, near Eagle Island!! This is an important data point since this small species (~12m) is probably the least known of the rorqual and has a conservation status of ‘Data Deficient’. It lives primarily in tropics/subtropic with confirmed sightings off Madagascar, Sri Lanka, Japan, Thailand, Australia, and now, Chagos. Its fun when science comes full circle 🥳🐋🙏 Thanks to @beth_seastheocean for great 📸s and excellent field observations! @ashadevos @clareembling @dr.dolphinsoup @bioacoustic_bebe @udayanga_zampath @dvharris_1 @plymbiomarsci @iomarinescience @officialzsl #charlesanderson @marinevertscru

When I was 22 and just embarking as a marine biologist a friend of mine got hold of a signed copy of the Blue Planet by the great Sir @davidattenborough . The signature was personalised to my name (with no spelling mistakes!) which I thought was remarkable for someone of his stature. Fast forward a few years and I get to be named in the foreword of Sir David and Colin Butfield latest book Ocean. I have yet to read the book in full (some will have noticed that red is not my usual shade of nail varnish). I have been told however that a signed copy is in the mail. Once it arrives I already know what I will do: I will head to the seacliffs near where I live, find a bench, look out toward the ocean, and turn the first page 🌊🙏 #oceanearthslastwilderness

A few highlights from a summer of highlights. Thank you friends and family for making it so special 🙏🙏🙏 And sorry for the stolen snaps 😅

Too scared to take photos on the wall yesterday 😱😬😳 - but we MADE IT!!! With a little @gruyere_aop cheese visit ! #ViaFeratta #Switzerland #gruyére #Moleson #fondue #cheeserecovery

📢 New Research Alert! Plastic pollution isn't just a coastal problem — even remote marine protected areas like the Chagos Archipelago are affected. Our new study, led by Dr. Jessica Savage @jessonmcsavage , finds microplastics in surface waters of reef manta ray (Mobula alfredi) feeding grounds. ❗ Key findings: 🧵 1.1 microplastic particles per m³ — mostly blue/black fibres 🧪 Over half were synthetic (e.g., polyester, nylon, polypropylene) 🌍 Egmont Atoll, an IUCN Important Shark & Ray Area, was the most contaminated These manta rays are already vulnerable due to slow life histories and fishing pressure; microplastics could add another layer of risk. 🧼 We recommend targeted beach cleans, local solutions like washing machine filters, and global action to reduce plastic waste. 📄 Read the paper: [link in bio] 👩‍🔬 2nd author: me! 📸 @jessonmcsavage and @mybucketlistfamily @plymuni @iomarinescience @royalholloway @officialzsl @tomletessier @heather.koldewey #Microplastics #MantaRay #MarineConservation #Chagos #PlasticPollution #MobulaAlfredi #MarineProtectedArea #OceanScience #NewPaper

Measuring 1 million fish 📏🦈 Over 14 years and by studying 20,000 hours of footage, a team led by our researcher @tomletessier has helped identify the best way to protect fish living along the seabed (benthic) like rays and midwater fish (pelagic) like sharks. #Sharks

Midwater fishes and sharks are more impacted by human pressure than their seabed-dwelling counterparts 🦈🐟 New analysis published in @sciencemagazine provides a roadmap to better protection of the open ocean and coastal ecosystems through a global size-based assessment of almost 1,000,000 fishes and sharks using underwater cameras Over 14 years, a team led by our researcher @tomletessier combined this data to study the effectiveness of marine protected areas for either fish living along the seabed (for example flounders, wrasses and rays) or swimming in the waters above (such as tuna, silky sharks and sardines). The results? Midwater (or pelagic) fish found near onshore markets were more likely to show signs of vulnerability and overexploitation from human fishing than their seabed (or benthic) counterparts. This finding has important consequences for those working to protect marine life across the globe as it: 🐟 Adds evidence that these pelagic ecosystems are less resilient to human pressure than their benthic counterparts – and require strong protection in order to recover 🐟 Highlights the need for caution around expanding already overexploited fisheries for pelagic sharks and sardines 🐟 Shines a spotlight on why international commitments, such as the UN’s Global Biodiversity Framework’s goals to halt and reverse biodiversity loss by 2030, can only be achieved through ensuring these vulnerable ecosystems are protected By better understanding the threats that wildlife faces and how human behaviour impacts ecosystems, we can take evidence-based action to restore the natural world 🌎 1, 2 & 4 📸 Manu San Felix 3 & 5 📸 Marine Futures Laboratory, @universityofwesternaustralia #Sharks #WildlifeConservation #Science

Just HOW exciting it is to see our work out today in @sciencemagazine is difficult to put into words. Pelagic and benthic fishes and sharks show divergent responses to protection along a human pressure gradient 🐟🦈🐠 Please share/read on link here /doi/10.1126/science.adi7562 and link in instagram bio What did we do? We used stereo baited-cameras #BRUVS to measure fish and shark body sizes in pelagic (in the midwater) and benthic (on the seabed) ecosystems. Then, we tested for differences in effectiveness of marine protected areas (MPAs) along a human pressure gradient What did we find?? (Side note - the collective effort that went into this is somewhat intimidating: 20,000 hours of underwater baited video from around the world to measure >800,000 individual fishes and sharks in pelagic and benthic habitats!) We found that fish body sizes in both pelagic and benthic ecosystems were bigger with remoteness and with greater protection. This was expected, and makes sense given what is known about vulnerability and protection effectiveness. However, for pelagics, MPA effectiveness was cumulative with remoteness, e.g remote MPA work best. This was in contrast to for benthic sizes, where the greatest effectiveness was found close to cities/markets. Put differently, while you get more bang for your buck the more remote your MPA is for pelagics, the opposite is true for benthics, which show increasing return near markets. Why does this matter? Many pelagic sharks and fish populations are at historically low levels. Our work shows that reversing this trend is possible but requires highly protected MPAs placed in remote locations, including on the High Seas, where efforts are lacking. Conversely, many tangible benefits for benthic ecosystems can be achieved in coastal regions near market/cities, from initiatives like habitat restoration and highly protected MPA. This has been such a fun analysis to do, and an honour to work with such an incredible team! DM if you can't access 1/ deploying BRUVS in French Polynesia 📸 @manusanfelix 2/ prep of BRUVS in Cape Verde 3/ BRUVS-stills of fish sizes 4/ locations of sites

🐬💩 𝐃𝐨𝐥𝐩𝐡𝐢𝐧 𝐏𝐨𝐨 could save coral reefs?! Thanks to some brilliant research conducted by @zsllondonzoo @tomletessier we now know these wonderful creatures help our beautiful coral reefs... with their poop! Listen to Ep1 of Saving Planet Earth to find out exactly how - available via the link in my bio, or wherever you get your podcasts 🎧    P.S who thinks @iamradzi needs his own poop smelling show?! 🙋🏻‍♂️     #dolphins #ecofriendly #nature #climatechange #climateaction #savingplanetearth #coralreef

Fun afternoon meet with @james_stew to talk about dolphin poo 🐬💩 and climate change 🌍, and all the marine wonders that make me optimistic about the future!

📷 Claire Collins ‼️New paper alert‼️ How did illegal fishing activity change during the pandemic?? Our latest correspondence in Current Biology paints a worrying pictures…. Link below and in insta bio- dm me for a pdf /current-biology/fulltext/S0960-9822(23)00854-0