FIELD NOTES: Panama

By Sara Swaminathan, postdoctoral scientist. This story originally appeared in the Winter 2025 edition of Transect.

"I like studying fish because they wake up late," my new colleague Matt Leray, a scientist at the Smithsonian Tropical Research Institute, joked as we sipped coffee on the deck of an 80-foot sailboat. A few days prior, a group of scientists and crewmembers, and a member of an Indigenous group that stewards the surrounding waters, had gathered on the ship and embarked from Bocas del Toro, Panama. We sailed to Isla Escudo de Veraguas, where we anchored offshore, waiting for the fish to wake up.

Matt's comment initiated a scuffle, as we were jolted from our reverie and reminded that there was lots of work to do before the fish woke up. Datasheets were attached to dive slates, wetsuits were donned, batteries inserted into cameras, and transect tapes and PVC quadrats tossed onto the dinghies used to navigate to our sites. This trip was the first assignment in my new role as a postdoctoral scientist with Senior Research Scientist Doug Rasher at Bigelow Laboratory. We were there for a collaborative, NSF-funded project led by Doug that aims to reveal how the feeding preferences of algae-foraging fish, which help maintain the ecological balance of coral reefs, may shift as reefs degrade.

I spent the morning with colleagues from UC Santa Barbara and UT Austin conducting fish behavior surveys, or "fish follows." With a stopwatch and datasheet at the ready, we snorkeled behind herbivorous fish, recording their every move. Were they eating the short, grass-like turf algae that quickly colonizes available substrate? Or were they interested in the taller stands of macroalgae that sway with the current? How many bites did they take before looking around warily for potential predators? As they fed, were they chased off by territorial fish, or did they chase off others themselves? Answering these questions will help us understand the competition and division of resources among different types of herbivorous fish, all unknowingly working together to keep the reef healthy. And illuminating how fish diets shift will help us predict the resilience of these important habitats to climate change globally.

Herbivores are important for maintaining balance in reef ecosystems because they feed on coral's primary competitor: algae. In Panama, we're studying two species of surgeonfish and six species of parrotfish, brightly colored fish named for the resemblance their mouths have to parrots' beaks. Those beak-like mouths are what make them so adept at grazing because some types of algae, like turf algae, can only be removed by scraping away the top layer of rock where the turfs grow.

Each fish follow lasted five minutes, but it felt like an eternity. Fish are fast. One glance away to record data could mean losing the fish completely, as they darted around the reef, quickly feeding and avoiding predators. Meanwhile, some members of our team conducted surveys of the algae and fish communities at our study sites. Others collected samples of fish and their prey for DNA sequencing and isotope analyses that will tell us what exactly they were eating, and ultimately, how good fish are at divvying up resources and keeping algae at bay.

After spending the daylight hours on the water, our team returned to the sailboat where we began dissecting our collections. This part was quite literally an "all-hands- on-deck" operation, with undergraduates and PIs seated side-by-side, separating stomachs from livers and preserving every piece of the fish to get as much information as possible. It was a flurry of activity and languages, as our multinational, multilingual team of scientists worked together to get the job done. The captain, Juan, kept spirits high by spinning an eclectic selection of salsa and bossa nova tracks.

Around 9 p.m., we all sat around a hearty dinner prepared by our incredible cook, Anjio, rehashing the day, laughing, and planning for the next one. It's good that the fish like to sleep in, because they had a way of keeping us up late, and we enjoyed every minute of it.

Photo courtesy of Juan Pablo Lozano Peña