The Last Sunset ... and Fish

As we all sit on the boardwalk to enjoy our last sunset at Palo Verde National Park, I couldn’t help but think back to just over a week ago, when I standing in the same place, fishing in the marsh for our last independent project. It was probably around 7:30 a.m.

            We were collecting fish at the Palo Verde protected marsh and also the outflow canal in the Bagatzí agriculture fields about 10km from Palo Verde. Our study aimed to see how agricultural landscapes may be affecting fish endurance and their response to predators. Why fish? For one, they are readily available at the rice fields and the marsh. But ultimately, because food production is so important worldwide, it’s important understand how our agriculture methods are affecting the environment around the land we cultivate. Agrochemical pollution is often seen in the ecosystems surrounding agriculture fields because of the intense use of pesticides, herbicides, and fungicides in crop growing. We sought out for some fish and results that could show how rice cultivation in Bagatzí is affecting them.

            Over a course of four days, we caught over one hundred fish and ran endurance tests to determine how long it took for them to become exhausted. We set up plastic containers as arenas for endurance tests, and used tongue depressors to follow fish around until they stopped swimming and were not responsive to the tongue depressor. We also noted how far each fish darted away when we first inserted the tongue depressor into the arena as well as measured their body lengths. After many hours of chasing fish and watching them jump out of the water during endurance tests, we got some results.

            The fish we collected from the rice fields were smaller than those from the protected marsh and also reached exhaustion faster. Bigger fish also tended to jump out of the water more than smaller fish, and also dart longer distances. Our results indicate that the agricultural landscape at the Bagatzí fields may be affecting fish size and endurance. Because we also found an association with jumping and darting with size, Bagatzí may also be indirectly affecting their ability to avoid predators.

            Besides a long paper that went along with our project, I gained a lot from our IP. It’s easy to pass on and agree with “pollution is bad” and “agrochemicals are bad”, but to go out into the field and actually find results of your own is incredible. Even if it was only four days; they were four, hardworking days that ended up telling a nice story we got to discover and write about ourselves. As I was looking out into the most beautiful sunset I was able to enjoy during our time at Palo Verde, I’m was saddened with the fact that only four days remain for me in Costa Rica. When will I be awake at 7:00a.m. for field work again? 
Yocelin Brito Bello
University of Illinois, Urbana-Champaign

Fish Fish Fish!

For the past week, we OTS students have been collecting, testing, analyzing and writing for our last independent project.  This time around, I, along with three other students decided to work with fish.  More specifically, Gambusia spp, a genus of primarily fresh water fish from the Poeciliidae family.

The premise of our project lies on the notion that because of the growing population on this planet, efficient agriculture has become more essential to meet the demands to sustain a growing population.  Agrochemicals are often used to produce higher yields in farming, however, they have negative impacts on the flora and fauna that come in contact with these chemicals.  In our study we compared predator avoidance behavior of Gambusia spp living in agriculture drainage canals from nearby rice fields with that of Gambusia spp from protected marshlands in Palo Verde National Park.  To examine predator avoidance behavior, we looked at initial flee distance, endurance, and aquatic jumping of the fish during our trials.

 Collection of Gambusia spp took place every morning on November 22, 23, 24, and 25, 2015 both at marsh and rice field sites.  After collection, fish were taken back to the station.  Each fish was placed into a plastic 15 liter container, containing 3 liters of water and left to acclimate in the container for 5 minutes.  After the acclimation time period, the tail of the fish was touched with a tongue depressor to measure the initial flee distance.  The time to stop darting was measured and was determined by when fish stopped darting away from the tongue depressor, and began swimming away at a constant speed.  Exhaustion was determined when fish no long swam away from the tongue depressor, and instead, the observer began pushing the fish with the tongue depressor.  Also, taken note was if the fish jumped out of the water anytime during the trial.  Finally, measurements of each fish were taken with a caliper.  The fish were held for 24 hours, and returned to their collection site, and new fish were collected daily.   After testing 115 fish for over 30 hours, data analyses suggested Gambusia spp from rice fields are smaller in length to ones from marshlands.  Initial flee distance and the act of aquatic jumping was also shown to be related to fish length and that Gambusia spp from rice fields reached exhaustion quicker than those from the protected marshland.

            We cannot specifically say that agrochemicals in the rice field water caused these significant differences, as we did not have the tools to measure if agrochemicals were present in waters or fish from the rice field, or protected marshland. Therefore, a variety of factors maybe the cause of our findings.  

Overall, this project was an enjoyable experience and a great way to end our semester at OTS. 

Jordan General

Duke University

Guaiacum sanctum

Our time at Palo Verde National Park has been concentrated on research.  I had never spent much time studying plants, so I had some reserves going into our faculty-led project about Guaiacum sanctum, an endangered evergreen species.  However, the more I learned about the species, the more interested I became.  The tree is different from many other dry forest tree species in that it is evergreen and has an odd age distribution.  In addition, it was fun to participate in the research.  I liked being part of a continuing project and helping to gather accurate data about an endangered species.

            A couple of my friends and I were interested in looking into the plant further, so, the following week, we decided to do our independent project about it.  We studied how age and light affects the plant’s functional traits.

            It was a cool experience.  It felt very official to go out and measure the trees, collect leaf samples, and take fisheye pictures of the canopy above each plant.  We wound up being able to collect information on many more trees than we had expected to and were able to get a pretty good picture of what the trees were like throughout the Palo Verde dry forest.  It was also interesting to be out collecting information on the plants that hadn’t necessarily been collected before.  Guaiacum sanctum is a species that has not been very thoroughly studied, so there are still many gaps in basic information about the plant.  Over the course of our four data collection days, we all developed an attachment to the plant that I hadn’t expected to feel.

            We wound up getting a lot of interesting results through our project.  For example, taller trees produce fewer leaflets, but put more resources into creating each one.  It was nice to be able to explain our results as well. In this case, that the larger trees had the resources to put into the leaves, instead of having to dedicate all their energy to ensuring that they had access to water and could survive the dry season.

            I would definitely like to spend more time learning about specific plants in the future.  Getting to study a plant at this level helped me to care about the species more than I thought I could, and I would like to have the same experience with other species. 

I think this mentality continues into a lot of conservation work: with education, people come to care about a species and its survival.  While most people won’t end up researching the species themselves, it is great to know that even informing people about their characteristics can produce such a change in perception.
Jessica Kuesel
Duke University