Chilean silversides

Chilean silversides are spawning in Iquique and Dichato

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 overnight trip by bus to Santiago 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 to 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.

IQ-embryos27hpf
The day of fertilization, the cell division in the fertilized embryos is beginning.

Cristian-pejerrey
Cristian Azocar recovering the gill net full of spawning ripe silversides

lecture-class
On 6 October 2025, Hannes gave a spontaneous talk in front of students and faculty of the Marine Science Department of the University Arturo Prat (UNAP) in Iquique

Hannes back in Chile to repeat common garden experiment!

25. September 2025. I have been asked by quite a few people (on both hemispheres), why I had to go again to Chile, to the same place, the same marine station, to repeat the same experiment from two years ago? Did the first fail somehow? No, not at all. The first experiment yielded really intriguing data suggesting similar local adaptation patterns in southern compared to northern hemisphere silversides.

But the catch is that one year could be a coincidence. To make statistically robust inferences about the nature of local adaptation in Chilean silversides, good science simply demands another, a second independent data set of observations. Even more so, because (i) the adaptation strength here is likely subtle, and (ii) some treatments and populations were indeed less successful the first time around.

And so I'm here again. The place where I spent 6 months during my sabbatical feels wonderfully familiar - despite being thousands of miles away from home. The setting September sun pours gold over the halfmoon-shaped Coliumo Bay. Spring is in the air here, but the little beach town is still mostly void of the summer crowds. I wander through the streets, recognize the stray dogs, and many of the people in this little village say they remember me and my family from two years ago.

In the marine station, the experiment is now being set up in a different location. Inside the aquarium, which is climate-controlled and therefore more suitable. It took us two years to gain permission to move in, and I had to have custom tanks made to set it all up. Will it all be worth it?

Now time is really tight, the setup needs to be put together in just a few days, because in the low latitudes of Chile's north, the spawning season of pejerrey has already begun. Fingers crossed.

buildup03
On 26 September 2025, Claudio Gallardo flexes off some tank material to make it fit

buildup02
Tight, but this is what will have to do!

buildup01
Plumbing begins in the Aquarium of the Marine Station in Dichato

A strong showing at the 47th Larval Fish Conference!

17 May 2024. Members of our Evolutionary Fish Ecology Lab had a blast attending this years 47th Larval Fish Conference in Huron, OH. Hannes, Emma, Max and alumnus Chris Murray (now at WHOI), went on a road trip from Connecticut to Lake Eerie to present and learn about all things larval fish. On Tuesday morning, the conference crowd enjoyed excursion or recreation options, all the while catching up with good old colleagues and making new connections and friends. A particular achievement: each of us presented research on a different fish species; while Hannes showed the first data emerging from his sabbatical research on Chilean silversides, Emma talked about baby California grunion development. Max presented a poster and two talks, the first about CO2 effects on the onset of schooling in Atlantic silversides and a second one one Black Sea Bass overwintering dynamics. Last, Chris Murray gave a fascinating first look into gene expression data from our most recent sand lance CO2 experiment. All around, a strong showing of our lab!
lfc47-banner-bold

Contributions from our lab to the 47th Larval Fish Conference in Huron, OH

  • Baumann, H., Gallardo, A., Gallardo, C., and Urbina, M. 2024. First evidence for countergradient growth variation in the Chilean silverside Odontesthes regia. Oral presentation
  • Siegried, E. and Johnson, D. 2024. Eyes bigger than your stomach: developmental inaccuracy in larval California grunion. Oral presentation.
  • Zavell, M.D., Mouland, M., Barnum, D., Matassa, C., Schultz, E.T., and Baumann, H. 2024. Overwintering dynamics of northern stock Black Sea Bass, Centropristis striata, juveniles. Oral presentation.
  • Zavell, M.D., O'del, J., Mouland, M., Webb, J.F., and Baumann, H. 2024. Ontogeny of larval schooling and effects of ocean acidification in Atlantic Silversides (Menidia menidia). Oral presentation.
  • Murray, C.S., Jones, L., Siegfried, E., Zavell, M.D., Baumann, Z., Wiley, D., Therkildsen, N., Aluru, N., and Baumann, H. 2024. Examining the effect of ocean acidification on hatching enzyme gene expression in Northern sand lance (Ammodytes dubius). Oral presentation.

LFC47-7
Long-time attendees of the LFC happy to meet again (fltr: Pascal Sirois, Dominique Robert, Hannes Baumann, Chris Chambers, Bill Leggett)

LFC47-1
Proud members of the lab at the end of the LFC47

LFC47-2
Extensive fields of water lilies in the Huron River, OH

LFC47-6
A nice break from conference science, kayaking the Huron River

LFC47-4
A very relaxing morning with great weather

Hannes returns from Chile!

 

16 April 2024. After a 9-month sabbatical stay at the University of Concepcion in Chile, Hannes returned to US soil today, full of experiences, data, and a chest full of samples of larval, juvenile, and adult Chilean silversides. Grateful to the many helpful colleagues and friends, a first year of experiments are in the bag, resulting in a number of interesting findings that await further analysis and - crucially - a second, replicate experiment in the year to follow. In other words, while the sabbatical is now over - the project of revealing co- and countergradient variation in the Chilean silverside is still very much underway. On to the next chapter!

hb-Puda
The cove of Puda near Dichato to the north of Concepcion, Chile

UConn Today reports on Hannes’ Chile research

This article has been reposted from UConn Today. Read the original here

October 12, 2023 | Elaina Hancock - UConn Communications

Snap Shot: How Will Organisms Adapt to Climate Change?

A UConn Marine Sciences researcher is spending time in Chile studying an important forage fish, and how this vital part of the food chain will adapt to a changing climate

13 - Pude
The rocky and picturesque shores of the Pacific near Dichato

The world’s oceans have experienced record heat in 2023. With rising temperatures and increasing acidification, we don’t yet know the full extent these changes will have on marine ecosystems.

UConn Department of Marine Sciences Associate Professor Hannes Baumann studies fish, including important forage fishes such as sand lance and silverside, to see how they adapt to changes in environmental conditions. Many species are already adapted to temperature gradients that exist across latitudes on Earth, and Baumann believes that from these patterns, we can learn how fish may adapt to climate change – in time. This so-called “Space-for-Time” approach is one tool scientists use to predict the long-term consequences of climate change.

As part of his post-doctoral work, Baumann experimentally found similar climate adaptation patterns in Atlantic and Pacific silversides. He suspects that a higher-order relationship exists between the strength of adaptation and the strength of the underlying climate gradient.

Now, with a grant from the National Science Foundation, Baumann has the opportunity to return to and expand his study of silversides to a South Pacific species and study how they are adapted to their coastal latitudinal temperature gradient.

“We are hoping the prove the validity of a principle of evolutionary adaptation for the Southern Hemisphere. It will then allow us to compare and integrate the patterns with the silverside species from the Northern Hemisphere, which evolutionary ecologists have been studying for decades already,” says Baumann.

After a two-week proof-of-concept trip to Chile in the Fall of 2022, Baumann established connections with local fishermen and colleagues at the Universidad de Concepcion in Dichato, Chile.

“To get spawning fish, we visit fish markets – called here caletas de pescadores – and first establish a connection to those who make a living catching silversides (“pejerrey del mar”). We’re making friends to explain our unusual request to accompany a fisherman during the night. This is the best method to make sure that the eggs get fully fertilized," he says.

In the Summer of 2023, Baumann began his yearlong sabbatical and has now moved to Chile for five months to begin the main experimental work on Chilean silversides, their adaptations, and the strength of those adaptations to underlying climate change.

01 - HB-Tongoy
Hannes in Tongoy near Coquimbo/Chile

Hannes starts sabbatical research in Chile

17 Juli 2023. Hannes just moved for 5 months to a small village called Dichato near Concepción in south-central Chile to build and then conduct a large common garden experiment on the Chilean silverside Odontesthes regia.

It's still early, disorienting days - but thanks to the ever optimistic Mauricio Urbina, the collaborator on this project, the mood is good and full of anticipation.

Want to learn more? The Chilean silverside page has it.

Dichato-from-above
Sun over Dichato at Coliumo Bay on 22 July 2023

Dichato-boats
Fishing boat in Dichato. In the background is the Marine Station.

urchin
A dead purple sea urchin