Our first Independent Projects of the course happened in Palo Verde National Park. We had lots of support from the professors, but the design and execution of the project was all up to the group. I was in a group of three, colloquially called “Team Fish.” As the name suggests, our project was studying fish, specifically looking at the effects of an agricultural landscape on the health and behavior of a common species of fresh water fish, Poecilia gillii.
We caught fish each day from three different locations, each with different water quality and would return them to their homes within a day. One site was inside Palo Verde National Park in the marsh directly in front of the station, and the other two sites were in the rice fields of the Bagatzí Agricultural project right outside the park. The rice fields are irrigated with water from Lake Arenal, and we collected the fish from these inflowing irrigation canals, as well as from the outflowing drainage canals where the water drains from the fields.
Once the fish were collected, they were put through a test of their anti-predator behavior. We scared the fish with a very artistic and terrifying Great Egret on a stick, and timed how long it took the fish to reach a large shaded area and where they crossed in relation to the researcher. After their behavior exams, the fish went to the photo shoot portion of their time with us. They were often very reluctant models, but despite the trials of working with diva fish, we got good pictures. We analyzed these pictures to get the length of the fish and to measure how much of the red-orange pigment called carotenoids they had in their ventral fins. This pigment is important in immune system functions as well as ornamentation, and can be used as a way to measure health. After a long day of testing, photographing, and analyzing fish photos, Team Fish would return the marsh fish to their home and stay to watch the sunset on the pier.
All of our hard work paid off, and we found out some interesting things. The health of the fish, as measured by the level of carotenoids found in their fins, was affected by an agricultural landscape. The fish from the marsh had the most carotenoids and the fish in the outflow canals had the least, leading us to believe that the difference could be because of the presence of agrochemicals in the water. The anti-predator behavior was not affected by the agricultural landscape, with outflow fish taking longest to reach shelter and inflow fish taking the shortest. This difference could be caused by the difference in the abundance of predators at each location, but is not likely due to agrochemicals.
Finishing the independent project and looking back on all the work we accomplished in such a short amount of time was a great feeling. We started the project a week before with our only plan being that we wanted to catch fish in the rice fields, and ended up a week later with an interesting question, a strong understanding of the topic, and interesting results to share. As we worked on the final papers and packed up to leave for San Jose, Team Fish and the rest of the group went to watch the sunset from the marsh for the last time.
Living with a host family is such a different experience than what we’ve done so far. We have our own rooms, get to navigate the city buses to get to class, and talk in Spanish a lot. I can tell my Spanish has improved in just the three days I’ve been here. With such a big change, it’s easy to forget what I was doing just a few days earlier. Yet sitting on the terrace at my host family’s house and watching the sunset over the city with the family dogs by my side, I think of all those great sunsets with Team Fish in the Palo Verde marsh and am proud again of all that we accomplished.