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John Hlavin @marinebiojohn.bsky.social · Aug 5

Oh my gosh that’s really cool! Thank you for inspiring it!

John Hlavin @marinebiojohn.bsky.social · Aug 5

Doing really well! Completely lucked out stumbling into the world of shark ecology under some really great mentors, including David! Got excited seeing your name pop up on my feed, I’ll always remember your class, so unique compared to the rest of the bio courses I took! How are you?

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John Hlavin @marinebiojohn.bsky.social · Aug 5

Woah, crazy collision of past and present worlds!! @caraocobock.bsky.social taught me an absolutely awesome course on biological anthropology at ND! Fall 2019 if I’m remembering correctly

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John Hlavin @marinebiojohn.bsky.social · Jul 10

Thanks David! The trap fisheries will not be thrilled if true 😅

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John Hlavin @marinebiojohn.bsky.social · Jul 10

We swabbed their bums for trace amounts of fecal DNA, and when tiger sharks voluntarily regurgitated some material during working ups (as they are known to occasionally do) we opportunistically collected that vomit too! No pumped stomachs here 🐅🦈

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Reposted by John Hlavin

Carylanne Joubert Maier @carylanneejmaier.bsky.social · Jul 10

#AES25 #JMIH25

Finally, @marinebiojohn.bsky.social John Hlavin, Reconstructing diets of Tiger Sharks in South FL

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John Hlavin @marinebiojohn.bsky.social · Jul 10

Thanks Carlyanne!! 🐅🦈

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Reposted by John Hlavin

David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · Jul 10

@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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Reposted by John Hlavin

David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · Jul 10

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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John Hlavin @marinebiojohn.bsky.social · Jul 4

Thanks for sharing!!

Reposted by John Hlavin

Erin Spencer, PhD @etspencer.bsky.social · Jun 27

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...

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...

link.springer.com

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John Hlavin @marinebiojohn.bsky.social · Jun 27

Maybe this is an appropriate step for prestigious high impact journals like Nature, which should be the epitome of rigor and which young scientists may not be targeting right away anyway, but it might further dissuade that “deep three pointer” attempt. Anyway, thanks for prompting this!

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John Hlavin @marinebiojohn.bsky.social · Jun 27

I look at peer review like refining precious metals. Initial submissions should be allowed to be lumps of (well-reasoned and ethical) ore. When researchers are young or venturing into a new discipline/method, initial submissions open to scrutiny might discourage ventures beyond comfort zones.

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John Hlavin @marinebiojohn.bsky.social · Jun 27

So with that in mind, I think there’s already an inner voice of imposter syndrome whispering doubts of whether my published work will impress the veterans in my field enough. So for those vets to also be able to scrutinize a paper in its infancy is intimidating and might poke that insecurity.

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John Hlavin @marinebiojohn.bsky.social · Jun 27

Yes, actually! Most if not all of it does resonate with me! Thank you for the thoughtful response. I think my initial hesitation comes from a place of being a very early career scientist with only a few experiences of having my own work reviewed / being a reviewer.

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John Hlavin @marinebiojohn.bsky.social · Jun 26

All for double blind/disclosing reviewer identities, but total transparency of initial submissions, revisions, and comments/responses feels a bit like making artists hang their scrapbooks up next to their masterpiece… interested in your thoughts!

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Reposted by John Hlavin

joeymaier 🌊 @joeymaier.bsky.social · Jun 26

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...

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Reposted by John Hlavin

joeymaier 🌊 @joeymaier.bsky.social · Jun 20

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...

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.

www.discoverwildlife.com

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Reposted by John Hlavin

spencer roberts 🦈 @unpopularscience.bsky.social · Jun 16

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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John Hlavin @marinebiojohn.bsky.social · Jun 16

Using multi-tissue stable isotope analysis, we show that they strongly depend on the nursery for their first two years before switching to coastal foraging, initially only seasonally in subadults who use more bay resources during the wet season when adults are more abundant in local coastal areas 🦈

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John Hlavin @marinebiojohn.bsky.social · Jun 16

🚨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/...

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....

onlinelibrary.wiley.com

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John Hlavin @marinebiojohn.bsky.social · Jun 13

🙋🏻‍♂️

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John Hlavin @marinebiojohn.bsky.social · Jun 12

🚨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...

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...

doi.org

Reposted by John Hlavin

David Shiffman, Ph.D. 🦈 @whysharksmatter.bsky.social · May 24

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...

www.frontiersin.org

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John Hlavin @marinebiojohn.bsky.social · May 23

The sharks would probably hear you wishing them a great weekend better if you slammed their tank shut after

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