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.