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Dr. John Hlavin

@marinebiojohn.bsky.social
1.8K followers 152 following 45 posts

🦈 Eckerd College Asst Prof of Marine Science 🔱 scapelab.eckerd.edu 👨🏻‍🔬 dr.johnhlavin.com 🦦 Monterey Bay Aquarium Ambassador

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Reposted by Dr. John Hlavin
Jenny Staletovich @jenstaletovich.bsky.social · 29/09/2026
Biscayne Bay provides a critical refuge for sharks and rays, new global study finds www.wlrn.org/environment/...
wlrn.org
Biscayne Bay provides a critical refuge for sharks and rays, new global study finds
A first of its kind shark and ray mapping effort found the bay, along with waters off the southern Everglades and a tiny South Florida key play an essential part in their survival. “Biscayne Bay is Mi...
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IUCN SSC Marine Conservation Committee (MCC) @sscmarine.bsky.social · 26/09/2026
NEW PUBLICATION ALERT Read the latest publication released by the IUCN SSC Shark Specialist Group with an update on the Important Shark and Ray Areas (ISRA) project: North American and Caribbean Atlantic: A regional compendium of Important Shark and Ray Areas Read here: doi.org/10.59216/ssg...
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IUCN SSC Shark Specialist Group @iucnshark.bsky.social · 25/09/2026
NEW PUBLICATION ALERT | 259 important shark, ray, and chimaera habitats mapped across North America and the Caribbean New additions to the global ISRA eAtlas reveal major migration corridors, nursery grounds, and aggregation sites across Atlantic, Caribbean and Pacific waters.
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IUCN SSC Shark Specialist Group @iucnshark.bsky.social · 25/09/2026
Find the full press release here: iucnssg.org/259-importan... Read the compendium here: doi.org/10.59216/ssg... See the eAtlas here: sharkrayareas.org/e-atlas/ You can watch the ISRA workshop video here: youtu.be/Z-ZmG7i8-QY?...
doi.org
North American & Caribbean Atlantic: A regional compendium of Important Shark and Ray Areas - Important Shark Ray Areas
ISRA REGION 4 – NORTH AMERICAN AND CARIBBEAN ATLANTIC REGION A REGIONAL COMPENDIUM OF IMPORTANT SHARK AND RAY AREAS
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Methods in Ecology and Evolution @methodsinecoevol.bsky.social · 21/08/2026
📖 Published📖 The superposition method for the reconstruction of food webs 🕸️ 🧪 🌏️ besjournals.onlinelibrary.wiley.com/doi/10.1111/...
besjournals.onlinelibrary.wiley.com
The superposition method for the reconstruction of food webs
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Reposted by Dr. John Hlavin
University of Miami Rosenstiel School @miamirosenstiel.bsky.social · 20/05/2026
A fish hideout you can't unsee, via @drcatmac.bsky.social @emilyyeager9.bsky.social @mantatrust.bsky.social and Marine Megafauna Foundation.
news.miami.edu
The Ocean’s weirdest pit stops: Scientists discover remoras hiding inside manta rays
Researchers documented remora fish diving into the cloacas and gill cavities of manta rays, revealing a bizarre marine behavior
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Dr. John Hlavin @marinebiojohn.bsky.social · 15/05/2026
My (future) department at Eckerd College is hiring again this upcoming cycle: tenure-track Assistant Professor of Marine Science focusing on marine mammalogy 🐬🐋🦦🦭 eckerd.exacthire.com/job/198479
eckerd.exacthire.com
Eckerd College
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Reposted by Dr. John Hlavin
Mindy Weisberger @laminda.bsky.social · 13/05/2026
Biologist @flammanglab.bsky.social at NJIT studies remoras & had some thoughts on their butt-hitchhiking (a hyphenate I've never typed before, but biology is full of surprises), saying that it might be because remoras are territorial & coprophagic (poop eaters) but mostly they're just big weirdos 🧪
people.com
Suckerfish Are Disappearing into Manta Rays' Rear Ends. Researchers Say They’re ‘Just That Weird’
Suckerfish, also known as remoras, have been observed diving into manta rays’ rear ends seven times over the past 15 years.
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Dr. Catherine Macdonald @drcatmac.bsky.social · 11/05/2026
In part, we wanted to invite people to get curious. Look at the weird stuff this fish is doing! Why is it doing that?! This is a paper I would absolutely love to talk to your eight-year-old about. So reminder: although science is serious and important, it’s also often incredibly weird and fun.
onlinelibrary.wiley.com
Hiding in Plain Sight: Evidence of Echeneidae Cloacal and Gill Diving Behavior in Manta Ray Hosts
Here we document seven observations of Echeneidae cloacal diving behavior in manta rays and one observation of gill attachment behavior. These observations span all three currently described species ...
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Reposted by Dr. John Hlavin
Dr. Catherine Macdonald @drcatmac.bsky.social · 11/05/2026
My amazing PhD student @emilyyeager9.bsky.social has a new paper out today on a behavior by remoras we have called “cloaca diving,” which makes for a lot of light-hearted content (fish going up manta ray butts will do that). It was an incredibly weird and fun paper to support her in writing.
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Emily Yeager, PhD @emilyyeager9.bsky.social · 11/05/2026
Looking for some weird science to brighten your Monday? Check out our new paper on remora cloacal diving behavior in manta rays published today in Ecology and Evolution! onlinelibrary.wiley.com/doi/10.1002/...
onlinelibrary.wiley.com
Hiding in Plain Sight: Evidence of Echeneidae Cloacal and Gill Diving Behavior in Manta Ray Hosts
Here we document seven observations of Echeneidae cloacal diving behavior in manta rays and one observation of gill attachment behavior. These observations span all three currently described species ...
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Reposted by Dr. John Hlavin
Johann Mourier @sharkmourier.bsky.social · 11/05/2026
Interesting! We also observed this behaviour in 2017 in French Polynesia! But we were not able to publish it. It means that this behaviour is widespread across oceans! See below our observation:
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Scientific American @sciam.bsky.social · 11/05/2026
The practice of “cloacal diving” could help remoras hide from predators—it could also be a feeding strategy or help the fish hitchhike
scientificamerican.com
Sucker fish are hiding in manta rays’ ‘butthole,’ new study reveals
The practice of “cloacal diving” could help remoras hide from predators—it could also be a feeding strategy or help the fish hitchhike
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Reposted by Dr. John Hlavin
Jason GRIZZLED Bittel @bittelmethis.bsky.social · 11/05/2026
So, uh. Sometimes, when a remora gets scared... It hides inside a manta ray's butt. Science 🧪 by @emilyyeager9.bsky.social @drcatmac.bsky.social, with a healthy HT to @whysharksmatter.bsky.social! www.nytimes.com/2026/05/11/s...
nytimes.com
A Fish That Hitches Rides Where the Sun Doesn’t Shine
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 11/05/2026
God forbid a manta ray have hobbies
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Chris Baraniuk @chrisbaraniuk.com · 11/05/2026
🎵 when a fish needs a ride in a manta ray's backside, that's remora!!! 🎵
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 11/05/2026
But seriously though I have seen a lot of crazy images in my career, representing a lot of crazy animal behaviors. This is the one that made me yelp the loudest when I first saw it.
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Dr. John Hlavin @marinebiojohn.bsky.social · 04/05/2026
🚨New 🦈 paper🚨 by Jack Elstner and team shows how nursery associated white sharks around San Diego responded to an anomalous tropical storm. Add extreme weather to the lengthy list of dynamic drivers of shark nursery function ⛈️ doi.org/10.1186/s404...
doi.org
A rare tropical storm event drives partial nursery evacuation by juvenile white sharks, followed by rapid aggregation reformation - Movement Ecology
Movement Ecology - Extreme weather events, such as tropical storms, can pose profound disruption to nearshore marine environments. Although coastal ecosystems are particularly vulnerable to storm...
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Reposted by Dr. John Hlavin
Erin Spencer, PhD @etspencer.bsky.social · 03/05/2026
Horrible, horrible news out of USF marine lab. Thankfully, no one is believed to be injured. But the fire today likely "total loss" -- thinking of all our colleagues who are grappling with the loss of their labs, gear, samples, and their research "home" 🐟🌍🌊🐙 www.tampabay.com/news/educati...
tampabay.com
Fire breaks out at USF St. Pete Marine Science Lab. Building likely ‘total loss’
More than 60 units and 200 firefighters were called to the scene.
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Dr. John Hlavin @marinebiojohn.bsky.social · 28/04/2026
Very excited to announce that I successfully defended my PhD yesterday! Immensely grateful for @drcatmac.bsky.social for being the most incredible and supportive advisor that any grad student could hope for. They say an advisor makes or breaks the grad school experience, safe to say she made mine
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Dr. John Hlavin @marinebiojohn.bsky.social · 24/04/2026
🚨NEW🐠PAPER🚨 The fine-scale ecological data needed to identify marine nurseries are a luxury not affordable across all management or conservation contexts. Here we propose a decision-based tool to facilitate precautionary nursery identification and management! Open access! doi.org/10.3389/fmar...
doi.org
Frontiers | A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management
Many marine species depend on nurseries during early life stages to promote growth and increase survival to maturity, supporting stock replenishment and stab...
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Reposted by Dr. John Hlavin
Erin Spencer, PhD @etspencer.bsky.social · 02/04/2026
The final chapter of my PhD is published in Journal of Experimental Biology! And, we got the cover! We used biologgers to estimate great hammerheads' temperature “sweet spot.” We saw they can perform well at a range of temps, which supports observations from the field. (1/2) 🌊🦑🧪🐟
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Science X / Phys.org @sciencex.bsky.social · 25/02/2026
Global analysis shows vessel traffic can disrupt behavior, communication, and stress physiology in marine megafauna, with potential long-term effects on population trends and conservation status. doi.org/hbqm4z
phys.org
Boat traffic alters marine megafauna behavior, stress and population trends, global analysis finds
A new study provides a comprehensive global synthesis of how vessel traffic affects large marine wildlife, including whales, dolphins, seals, manatees, sea turtles, sharks and rays.
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Dr. John Hlavin @marinebiojohn.bsky.social · 25/02/2026
⚠️NO WAKE SCROLL ZONE⚠️ 🚤Proceed reading at idle speed⛴️ New meta-analysis from @juliasaltzman.bsky.social untangles the effects of vessel disturbance on marine megafauna, published open access in npj Ocean Sustainability! doi.org/10.1038/s441...
doi.org
Charting the course for management: a global analysis of effects of vessels on marine megafauna - npj Ocean Sustainability
npj Ocean Sustainability - Charting the course for management: a global analysis of effects of vessels on marine megafauna
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Dr. John Hlavin @marinebiojohn.bsky.social · 28/01/2026
ICYMI (it being my most recent research publication) ⬇️
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Reposted by Dr. John Hlavin
Emily Yeager, PhD @emilyyeager9.bsky.social · 23/12/2025
Another new publication! Congrats @juliasaltzman.bsky.social
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Dr. John Hlavin @marinebiojohn.bsky.social · 23/12/2025
🚨NEW 🐟 PAPER 🚨 On this episode of unusual animal friends… @juliasaltzman.bsky.social was in the right place at the right time to record and generate an ethogram of a stingray-cobia pair, an interaction fishers have relied on to find and sight-fish for cobia! onlinelibrary.wiley.com/doi/10.1111/...
onlinelibrary.wiley.com
Behavioral Evidence of Predator–Predator Commensalism: Cobia Track and Feed on Prey Disturbed by Southern Stingrays
We documented a novel predator–predator commensal foraging interaction between cobia (Rachycentron canadum) and a southern stingray (Hypanus americanus) in a shallow coastal habitat of Biscayne Bay, ...
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Reposted by Dr. John Hlavin
Emily Yeager, PhD @emilyyeager9.bsky.social · 18/12/2025
Check out our new publication on the growth rates and habitat use of nurse sharks in Biscayne Bay, FL compared to nearby Bimini, Bahamas which came out today (open access) in Environmental Biology of Fishes! link.springer.com/article/10.1...
link.springer.com
Is the seagrass greener on the other side? Faster growth in Biscayne Bay, Florida’s nurse sharks (Ginglymostoma cirratum) compared to neighboring conspecifics of Bimini, The Bahamas - Environmental Bi...
Effective management of vulnerable species requires a precise understanding of life history. In 2024, Fadool et al. published the first von Bertalanffy growth model for the nurse shark (Ginglymostoma ...
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 18/12/2025
Hypothesis: better Cuban food
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Dr. John Hlavin @marinebiojohn.bsky.social · 18/12/2025
🚨New 🦈 paper🚨 Who would have thought that only 80 km of separation across the Straits of Florida would be enough to create significant differences in age and growth of Atlantic nurse sharks? Well… now us! Curious? Open access article linked below link.springer.com/article/10.1...
link.springer.com
Is the seagrass greener on the other side? Faster growth in Biscayne Bay, Florida’s nurse sharks (Ginglymostoma cirratum) compared to neighboring conspecifics of Bimini, The Bahamas - Environmental Bi...
Effective management of vulnerable species requires a precise understanding of life history. In 2024, Fadool et al. published the first von Bertalanffy growth model for the nurse shark (Ginglymostoma ...
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Dr. John Hlavin @marinebiojohn.bsky.social · 15/12/2025
New Manta paper!!! Congrats and great work, Emily! 🥳 Open access and linked below doi.org/10.1007/s002...
doi.org
Stability and spatial variance of Mobula yarae-associated fish aggregates in South Florida - Marine Biology
Despite their importance to organismal and ecosystem function, symbiotic associations in marine environments are often poorly understood. In the case of manta rays, casual and temporary associations w...
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Reposted by Dr. John Hlavin
Carylanne Joubert Maier @carylanneejmaier.bsky.social · 10/07/2025
#AES25 #JMIH25 Finally, @marinebiojohn.bsky.social John Hlavin, Reconstructing diets of Tiger Sharks in South FL
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 10/07/2025
@marinebiojohn.bsky.social at #JMIH25 #AES25 A multi-method approach can help determine the diet of tiger sharks, different methods have pros and cons. Includes data from 67 Tiger sharks- I think I helped get data on 6 of these!
John’s title slide showing a juvenile tiger sharks
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 10/07/2025
Whoa- @marinebiojohn.bsky.social found *cow* and *pig* among tiger shark diet. (He thinks they were bait in lobster and crab traps)
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Erin Spencer, PhD @etspencer.bsky.social · 27/06/2025
This was a HUGE effort with LOTS of field time and LOTS of analysis – huge thank you to all my coauthors and the many folks who contributed in the field. Very proud of this one. (4/4) @dr-yannis.bsky.social 🦑🧪🌊🐟 See the paper: link.springer.com/article/10.1...
link.springer.com
Energetic benefits of prey choice for a shark-eating shark - Oecologia
Optimal foraging theory has been used to understand the foraging choices of animals but is rarely applied to large predatory fishes due to difficulties measuring their behavior in the wild. Great hamm...
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joeymaier 🌊 @joeymaier.bsky.social · 26/06/2025
Further coverage, this time by @forbes.com columnist & #shark researcher @melissacmarquez.bsky.social, about the new paper on #hammerheadsharks using #BiscaneBay, #Florida as a #nursery Column quotes @drcatmac.bsky.social www.forbes.com/sites/meliss...
forbes.com
How Miami’s Waters Are A Lifeline For Hammerheads
A study from the University of Miami reveals great hammerhead sharks use Biscayne Bay through multiple life stages, despite growing environmental pressures.
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joeymaier 🌊 @joeymaier.bsky.social · 20/06/2025
A new post from DiscoverWildlife covers the 2025 research from @marinebiojohn.bsky.social and @drcatmac.bsky.social showing tat #BiscayneBay is a nursery area for #hammerhead #sharks www.discoverwildlife.com/animal-facts...
discoverwildlife.com
A rare shark is seeking refuge in Miami's Biscayne Bay. Here's why scientists just spent 8 years tracking it | Discover Wildlife
A new study reveals that Biscayne Bay is a vital year-round nursery and seasonal refuge for one of the world's most endangered shark species.
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spencer roberts 🦈 @unpopularscience.bsky.social · 16/06/2025
This is wild: Recently, I spotted a critically endangered great hammerhead… in the middle of urban Miami. It wasn’t a fluke. @marinebiojohn.bsky.social & @drcatmac.bsky.social published a study today showing this bay — full of yachts, crab traps, & fishing boats — is a vital nursery habitat. 🌎🦑🧪
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Dr. John Hlavin @marinebiojohn.bsky.social · 16/06/2025
🚨NEW🦈PAPER🚨 Excited to announce my first publication with @drcatmac.bsky.social on the ontogenetic and seasonal trophic ecology of great hammerheads around the Biscayne Bay nursery! Linked below onlinelibrary.wiley.com/doi/10.1002/...
onlinelibrary.wiley.com
Nursery Resource Use Dynamics in Great Hammerheads (Sphyrna mokarran) Across Ontogeny
The ecological trade-offs required by nursery dependence are poorly understood. Using multi-tissue stable isotope analysis, this research provides evidence of constrained resource use in juvenile gre....
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Dr. John Hlavin @marinebiojohn.bsky.social · 12/06/2025
🚨NEW PAPER🚨 Congrats to @scrippsocean.bsky.social’s Jack Elstner and team on their new research demonstrating early successes in the application of AI-driven software Ocean Ruler as a citizen science tool for fisheries monitoring! doi.org/10.1007/s002...
doi.org
Ocean Ruler– an image-based, AI-driven approach to small-scale fisheries monitoring and catch size estimation - Marine Biology
The ubiquity of data-limited, data-absent, and unmanaged fisheries around the world illustrates a significant need for enhanced monitoring of living marine resources beyond conventional agency-led pro...
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 24/05/2025
Frontiers | Trophic and feeding ecology of whale sharks (Rhincodon typus) using bulk stable isotope analysis
frontiersin.org
Frontiers | Trophic and feeding ecology of whale sharks (Rhincodon typus) using bulk stable isotope analysis
IntroductionDespite their size, relatively passive behavior, and commercial significance, knowledge of the behavioral ecology of whale sharks remains limited...
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 10/05/2025
Our two days of “Shark scientist for a day” fundraiser trips raised $10,000 that will go towards providing low-resource Miami public schools with free marine biology field experiences in the future. Thanks to my 20 social media followers for joining us and supporting this important cause!
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Dr. John Hlavin @marinebiojohn.bsky.social · 02/03/2025
🚨 New paper 🚨 Go check it out! Way to go, Emily!
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Dr. John Hlavin @marinebiojohn.bsky.social · 19/11/2024
This was a “look Ma I made it” moment I wasn’t expecting this Tuesday morning. Thanks, David!
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David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · 14/07/2024
John Hlavin @marinebiojohn.bsky.social at #JMIH24 American Elasmobranch Society 🧪🦑🦈 Biscayne Bay is a nursery area for great hammerhead sharks. They start to leave between 140-170 cm in size, expanding their niche without abandoning coastal food sources, varying habitat seasonally.
John and his title slide
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Dr. John Hlavin @marinebiojohn.bsky.social · 21/02/2024
Hi Bluesky! PhD student here studying shark trophic ecology, with special focus on great hammerhead nursery use. I’ve had moderate success as a science communicator on Tiktok, Instagram, Snapchat so this is a new frontier for me. Excited to connect with y’all!
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