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Gabe reflects on his NSF-REU experience

Posted on July 16, 2026July 16, 2026 by Hannes Baumann

By Gabe Redmond

My experience over the course of this project and my time at this REU was incredible. Getting hands-on in fieldwork was a dream come true. I loved to work with creatures like the Atlantic Silversides, gain so much knowledge about them, how they grow, and how important they are to the ecosystem.

Doing the project was really cool and very fun. Getting to understand each step of the process until we reached our final goal was very cool and interesting. I really enjoyed being around a big group of people who were also intrigued and excited about what we were going to find. I had an amazing mentor who stood by constantly helping me and working right alongside me, and teaching me all the neat tips and tricks to everything, something I will never forget.

I got to meet so many incredible people and personalities, and being able to see the excitement, the concentration, and so much more is something that can’t be put into words. It’s this feeling that is so extravagant, having such a great group of people that I would consider friends was such an incredible honor to have worked alongside them. If any of them ever asked me to come back up and help any time during the future, I would come back and work with or for any of them.

I could not have asked for a better experience and I am very happy that I get to bring so much knowledge with me towards my future goals and all the friends and contacts with me as well.

NSF-REU experiment reveals surprising heat tolerance of silverside embryos

Posted on July 5, 2026July 7, 2026 by Hannes Baumann

3 July 2026. Just in time for America250 celebrations, we want to share our own small cause of joy and accomplishment. The team, NSF-REU student Gabe Redmon, graduate student Emma Siegfried, and Hannes Baumann, just finished the second and last experiment on Atlantic silverside embryo heat tolerance. The data will become part of a globally distributed experiment on fish embryo heat sensitivity (Thermal Ecology Alliance, P. Pottier), hopefully helping to reveal broader evolutionary and ecological patterns across taxa.

In the most work-intensive moments, the team could not have succeeded without the help of Hermione Lao (NSF-REU 2026), graduate students Vicky You & Hannah Roby, and Hiryu Shinand (undergrad). Thank you!

The general experimental design was straightforward to make it broadly adaptable across systems. The goal was to expose newly fertilized fish embryos to heat stress and quantify their mortality. Choose a presumed stressful range of temperatures, vary the duration of the exposure, assess it at two developmental stages (early vs. advanced). Generally, silversides make great model organisms; they have been studied for decades and repeatedly rose to fame for revealing novel eco-evoluationary patterns (e.g., Conover, Therkildsen et al., Akopyan et al., Murray et al.).

However, the thermal sensitivity of Atlantic silverside embryos had not yet been robustly quantified.

The project is a central part of Gabe Redmon's NSF-sponsored Research Experience for Undergraduates (REU, UConn-MysticAquarium, NSF #2349353). Gabe discovered early that 'straightforward' does not equal 'easy' or 'low effort'. First lesson; silversides don't particularly care about Mo-Fr schedules, they are on a moon schedule, which influences the tides. For good quality experiments, it is best to collect adults right before they spawn on full and new moons. And with all the events that than need to follow in short order; there simply is no way to avoid weekends. Luckily, Gabe was completely unflinched by any of that; his dedication and curiosity were outstanding. Together, we designed some novel rearing designs to allow tracking groups off embryos through hatching. Together, we went to Mumford Cove to collect spawning-ripe adults with a beachseine. Twice.

Together - and with the necessary portion of luck - we pulled it off.

The time to show you the data will come later, the time to show some pictures is now. The analysis, which turns numbers into patterns, which then may lead to new insights has only just begun. One thing, however, is already clear from these data; silverside embryos are surprisingly heat stress tolerant. Exposures of up to 4h to 27-34C produced no measurable increase in mortality.

But that's not the whole story. There is more to come.

For now, join me again in a big show of hands for the whole team and the many helping hands!

Hannes talks black sea bass at the University of British Columbia

Posted on March 15, 2026March 15, 2026 by Hannes Baumann

Vancouver, 15 March 2026. Hannes spent 3 beautifully intense days at the University of British Columbia, following an invitation by Profs. Andrea Frommel and Colin Brauner to talk at their Comparative Physiology seminar series about our soon to be published synthesis work on black sea bass overwinter migrations. Thank you Andrea, for the comfortable stay at your house and thanks to all the faculty and students who generously shared their time to meet and talk about our respective research experiences. Thank you, Colin, for showing me the aquatic research facilities and the biodiversity center!

Ambitious Experiment Discovers ‘Flipped’ Genetic Secrets of a Small Fish

Posted on March 9, 2026March 9, 2026 by Hannes Baumann

A grueling road trip led to an extraordinary experiment at UConn’s Rankin Seawater lab that discovered how inverted chromosomal segments help Atlantic silversides adapt

When a species lives in two distinct types of habitats, individuals with traits better suited to each habitat will thrive and reproduce, naturally selecting descendants with those traits. But what about mobile, aquatic species that live across a broad range of temperatures and latitudes? How do they maintain their genetic differences if individuals are free to mix and interbreed?

New research published on 5 March 2026 in Science finds that chromosomal inversions – which occur when a chunk of chromosome containing tens to thousands of genes breaks off, flips 180 degrees and reattaches to the same chromosome – play a central role in shaping these advantageous adaptations.

Read the whole story at UConn Today (9 March 2026)

Akopyan, M., Jacobs, A., Rick, J., Wilder, A., Baumann, Z., Conover, D., Baumann, H., and Therkildsen, N. (2025)
Multiple chromosomal inversions modulate continuous local adaptation along a steep thermal cline
Science 391:1015-1021

Hannes visits Emma’s sand lance experiment in Norway

Posted on March 9, 2026March 9, 2026 by Hannes Baumann

Austevoll, the world-famous marine research station, has also been PhD student Emma Siegfried's home for the past 2 1/2 months. Emma became the first US recipient of a European Union exchange fellowship (AQUASERV program) that covered the costs of her stay and her research in Norway. The goal of her project is to rear embryos of a local sand lance species, the Lesser sandeel Ammodytes marinus, under different levels of CO2 to then compare the results to what is already known for the Northern sand lance A. dubius on the western side of the Atlantic ocean.

Emma's experiment has been a success so far, thanks in no small part to the incredible help of our Norwegian collaborators. Every one at the station has been welcoming, friendly and eager to show us the large-scale aquaculture research on cod, halibut, haddock, plaice and many other fish species that is being conducted here every day of the year.

As we gape at the impressive tanks and installations, as we chat eagerly about deepening our collaborative ties and enjoy Norwegian hospitality and nature, we feel that this may indeed be the beginning of another great chapter of sand lance science to come.

Norwegian sand lance are hatching!

Posted on February 10, 2026February 10, 2026 by Hannes Baumann

By Emma Siegfried.

Austevoll, 10 February 2026. More than two months into my research stay here in Norway, things are going pretty well. Instead of one single experiment, we actually ended up running 3 separate experiments at once because the female fish took their sweet time to get ready to spawn.

As I learned, it is quite common in the tanks here that only a few females become ready to spawn at a time, which meant that a new trial had to be started again and again.

Our first spawn was now exactly 4 weeks ago, and I'm happy to report that our first embryos in the 10˚C treatment started hatching last week! Now we’re counting the larvae that are hatching each day, taking photos of them on the day of hatch and then also taking videos of their hearts to measure heart rate.

The hatchlings are then preserved, mostly in ethanol but also in RNAlater for potential further genomic and transcriptomic analyses.

The 2nd experiment & Hannes’ time in Chile end – but the science just started

Posted on December 21, 2025December 21, 2025 by Hannes Baumann

Whole Blog

22 December 2025. Shortly before Christmas, a cloudless blue summer sky stretches endlessly over Dichato. The summer vacationers now arrive in troves in this small Chilean village. Hannes just returned again for a few short days to help end the second common garden experiment at the Marine Station, preserve all sampled specimens, and ready them for their journey to Connecticut. The days are filled with bittersweet emotions, as one chapter ends while marking the beginning of the data analysis phase of the whole project.

For more than 5 weeks, research technician Tamara Cuevas diligently attended to the experiment while Hannes finished teaching his class at UConn. Tamara successfully executed the daily husbandry, feeding, testing, the frequent sampling events, while reacting nimbly to all the unforeseeable, yet inevitable things that came her way. Tamara, you're truly the hero of this second experiment, well done!

Meanwhile, Hannes used his third journey to the southern hemisphere to make a few stops along the way. In Lima (Peru), he met with Victor Aramayo, a biologist at the Peruvian Institute of Marine Research (IMARPE), to receive silverside samples from two locations in Peru. He then traveled to Valparaiso (Chile) to meet with Prof. Mauricio Landaeta (Universidad de Valparaiso), who contributed samples from the southernmost silverside species (Odontesthes smitti) from Punta Arenas in Chile's far south. He flew for a day trip to Antofagasta (Chile) to meet Prof. Marcelo Oliva (Universidad de Antofagasta) who contributed specimens from this particular locale. All together, we now have silverside samples from 7 populations spanning 45 degrees of latitude (9-54S) for genomic analyses!

As Hannes shakes hands and emotionally says good bye to his Chilean friends and colleagues, it is the excitement for the findings to come that shines as bright as the December sun over Dichato.

Saludos y feliz navidad!

Emma arrives in Norway to start sand lance experiment

Posted on December 18, 2025December 18, 2025 by Hannes Baumann

By Emma Siegfried

16 December 2025. Hi, Emma here reporting in from the Institute of Marine Research in Storebø, Norway! After a quick stop in Amsterdam, I landed in Bergen on Saturday morning. I grabbed a quick ferry to get over to the island and settled in over the weekend in one of the on-station residences. The area is pretty rural, but the surroundings are idyllic. The islands are exactly what you would expect to see out of a movie.

Yesterday, I was able to get a tour of the station, and the facilities here are incredible. If I had to estimate it’s probably 6 or 7 times the size of Rankin lab. The facility has been doing research on the early life history stages of Cod, Haddock and Plaice on top of previous work with Lesser Sand Lance (Ammodytes marinus) larvae, and as a result has some quite large broodstock tanks.

Hannes returns to the US, but the experiment continues!

Posted on November 9, 2025November 9, 2025 by Hannes Baumann

10 November 2025. The spring is now in full swing here in Dichato, and the days are getting steadily hotter and drier. The past 6 weeks flew by in a whirlwind of action, and with all the last minute preparation plus the vagaries of coordinated field sampling and larval rearing it definitely is with a little pride that I look back at all that we have accomplished in this short time.

We stood up the experimental setup in just a matter of days, with new tanks and in a new (better) location inside the main wet lab of the Dichato station (aka 'El Acuario'). We flew to Iquique for the October full moon and were rewarded with spawning ripe fish; and with similar ease sampled the Dichato population just two days later. A trip to the notoriously difficult Coquimbo region unfortunately ended without fish, but the sampling of the southernmost population in Puerto Montt was again timed almost perfectly for the November full moon.

All the while the setup withstood the reality test, and I taught Tamara Cuevas, a technician from the station, the many aspects large and small of the rearing methods. Tamara will now take over the daily rearing for one month, before I will return in mid December to help terminate the experiment and then take home all samples. All the best, Tamara, for your time as the main experimenter!

We are halfway through the rearing, fingers crossed that the second half will go as smoothly!

The Chilean silverside experiment begins to produce data!

Posted on October 29, 2025October 29, 2025 by Hannes Baumann

29 October 2025. While the fish from Dichato in the coldest treatment have just begun to hatch, their conspecifics from Iquique and Dichato growing at the warmest temperatures have already more than doubled their size at hatch and are therefore ready for a first length sample. This is always a particularly sweet and rewarding moment, when after all the work to get to this point - it now finally arrived.

In each rearing container, 80 fish remain to grow further, while the rest is sampled, preserved in ethanol and then measured via calibrated pictures. Then the size difference between hatch and the first time point is divided by the number of days to obtain our first growth rate estimates of the second experiment!