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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!

DI14-hatchday_5 — On 29 October, the embryos from Dichato are about to hatch in the 14C treatment

No luck in Caleta Sierra

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

Expanding the Silverside System | Blog

15 October 2025. While the embryos from Iquique and Dichato develop and now begin to hatch in the warmest temperatures, Hannes and Claudio took a quick trip to get embryos from a third population at ~ 30S. It's where the Chilean coast is as wild and rugged as anywhere else, but the trees have already given way to prickly shrubs and lots and lots of cacti - the desert begins. It's also the area around the big double city of Coquimbo/La Serena, where already in 2023 we ran into trouble finding pejerrey, let alone spawning ripe ones. Back then, we thought of it as an aberration, something surely owed to the strong El Niño phenomenon of 2023 - but nothing permanent.

IQ23hatch — Newly hatched Chilean silversides (*Odontesthes regia*) from the Iquique population

And so here we are again. And to our chagrin, again the fishermen in the Coquimbo fish market just shrug and point to the pejerrey they sell. No, those are not local at all; they are from the south of Chile in Puerto Montt.

So again we follow our instincts back to the small cove, where we had some (some!) luck the last time around - Caleta Sierra. Again we meet up with Mauricio Vega, the fisherman who wants to help us. And again we try at night and in the morning to row a gill net around a stretch of the small pebble beach of the cove and then pulling it ashore. We do catch all kinds of fish that way, just not the ones we are after! In total, the whole effort netted no more than five pejerrey, all but one unripe.

We return empty handed, pondering the truism that nature just doesn't care about science projects. To me, it seems timely to rethink whether this species truly has a continuous or perhaps discontinuous distribution along the Chilean/Peruvian coast.

Chilean silversides are spawning in Iquique and Dichato

Posted on October 8, 2025October 20, 2025 by Hannes Baumann

7 October 2025. Its been a truly wild last few days. In Dichato, we were racing against time to get all the setup ready, including an emergency bus trip overnight to Santiago to retrieve the missing chillers from a central aquarium store, and a Saturday morning frenzied work session to get everything up and running before the first sampling trip to the north. On Saturday night Hannes flew to the desert city of Iquique at 20S, a place of unreal beauty and harsh landscapes of sand, rocks, and ocean.

Thanks to the incredible help and expertise from local collaborators Prof. Miguel Araya and Dr. Cristian Asocars, the Sunday (5 Oct) morning fishing via gill net was almost too good to be true. With just one cast, we caught upwards of 400 Chilean silversides, all running ripe - perhaps inspired as we often found for northern hemisphere silversides - by the full moon. The fertilization in the boat and then transport of the embryos back to the lab via airplane all went without problems - a rare moment to cherish as an experimenter.

The kicker? The same full moon also appeared to entice the silversides in Dichato, and so a spontaneous fisherman went out with Hannes Tuesday night to - lo and behold - again catch all the fish, all running ripe, we needed to start the second population of the experiment.

48 hours. 2 populations more than thousand miles apart sampled and brought as embryos into the common garden experiment. Maybe I should consider a generous offering to San Pedro, the saint of the fishermen whose statue is in everything fishing harbor in Chile.