Two weeks, three field stations, and billions of bugbites later, the Bio FSP has emerged from the jungle and has internet access once again at La Selva Biological Station on the Caribbean slope.
There’s so much to write about, but I’ll take it one location at a time, starting with Cuerici.
The Cuerici field station is in one of the most beautiful places I have ever seen. We left Monteverde right after breakfast and drove to San Jose, where we left Ryan Calsbeek and picked up Matt Ayers, our professor for the middle third of the course. Then we drove another 2 hours or so (uphill all the way) until we were driving on the continental divide. Eventually our bus pulled over and we met Carlos and Alberto, our hosts at Cuerici. They drove our bags down to the Cuerici field station, and we followed them on foot with our backpacks. The hike in was about 4 km, mostly downhill, on a dirt road. We got to the field station right after dark.
The next day Carlos (who owns the property and runs the field station) led us on a hike up a trail he cut himself. The trail is a loop that starts at the field station and goes up through a section of secondary forest dominated by Alder trees and a species of bamboo. After about 15 minutes of walking we crossed into the primary forest, which has never been cut. Here we found 1000-year old oak trees growing side by side with orchids, bromeliads, and bamboo. Near the top of the trail is a lookout facing the pacific coast, from which you can see Chirripó, the tallest mountain in Costa Rica, as well as the Osa Peninsula, which is where Corcovado is located. Carlos’ family has lived on this land since at least his grandfather’s generation, so he knows it and its history inside and out. The mountains here remind me of home in a way, but they’re also so much higher and clearly newer – the view from the field station in the morning is almost always a vista of mountaintops floating above the clouds. The weather here is also different; it’s sunny in the morning, but clouds and fog roll in like clockwork around lunchtime. After lunch we’ve seen days that clear up again, but we’ve also had rainy afternoons. It’s colder here too – at night it can be below freezing, and windy.
After a break for lunch we gathered again so Carlos could show us the trout farm that he runs.
Apparently 70 years ago the Costa Rican government thought it would be a brilliant idea to introduce rainbow trout from Canada and the western US into high-elevation streams, but quickly found that they were detrimental to the endemic ecosystems.
They’ve since removed all the trout from the rivers here, but some still live in lakes where people can fish for them recreationally and the government still raises them in hatcheries as food.
Besides the government’s facilities, Carlos has the
only other rainbow trout fishery in Costa Rica.
While the government imports eggs from Washington state in the US, Carlos breeds his own fish and raises them, keeping some as reproductive fish, selling some to restaurants, some to the lakes that are stocked with trout, and keeping others to eat.
They’re kept in pools that are built into a hillside so that water can flow downhill from one canal to the next without using any electricity.
The water that flows through the system comes from a spring above the station, and once it’s gone all the way through the different trout pools it rejoins a stream that runs through a hydroelectric generator that Carlos built himself down the hill from the station.
The whole operation is so well planned and thought out, and all without most of the technologies used in the United States for the same purposes.
He’s been breeding fish for 22 years, without the help of books about fish husbandry or information from the Internet.
He also keeps cows, ducks, chickens, a horse, and a few dogs.
Apparently his family used to log the land, but they’ve stopped cutting trees from deep in the forest and instead use the Alder trees along the forest’s edge that regenerate quickly.
He’s clearly brilliant and probably taught himself most of what he knows, so it’s been quite the experience to talk to him about all his endeavors and experiences.
He also only speaks Spanish, so that’s been a lot of fun too.
We were so impressed by the fishery and so touched by how much Carlos clearly cares for the fish and his impact on the land that we decided to do our project on the trout.
We started out by asking him questions about the fishery and asking him what questions he has about raising the trout; about what he feeds them (commercial feed and sometimes worms from the compost), how many he has, whether he’s ever experimented with different densities in each pool, etc.
Turns out one of his biggest questions was just how the water temperature, dissolved oxygen, and pH has been changing.
Imagine running a fishery and not having the equipment to quantify DO, let alone water temperature!
Groups in past years have taken these measurements as their project, so we also measured these things aside from our project so Carlos can begin to have a year-by-year record of temperature, DO, and pH in the ponds.
Our real project, however, was built around the relationship between the relative growth rate of the fish and their densities.
We compared the trout’s body condition to the density of trout in their pond, and we (meaning mostly Maddy, the math major) also set up an economic model to show whether it’s more profitable to grow fish at higher or lower densities depending on their growth rate and the food they’re given.
The growth rates we used were based on a study of wild brown trout, so the model obviously isn’t perfect, but it was really interesting to see how density affected yearly profit—turns out in almost every scenario we imagined it was more profitable to grow the fish at lower densities.
In any case, we ended up spending two full days with Carlos, catching fish from each pool with a net, measuring their length and weight, marking them by clipping their anal fins, and releasing them back into their pool.
The next day we caught them again and used the number of marked fish we caught to estimate the total number of fish in each pond (something Carlos doesn’t know exactly).
Working with the fish was incredible – they’re absolutely beautiful, especially in the sunlight.
We put the fish we netted into a smaller tub, and each took turns hand-catching them from the tub and measuring them before returning them to the water, which was pretty amusing since some of them put up quite a fight.
On our last day Carlos caught 10 of the trout and cooked them up for lunch—only one of them was marked, which almost perfectly matched our population estimations for that pond!
Now that we have internet again I’ll try to catch up with posts about Corcovado and Las Cruces whenever I get a minute to write. Stay tuned!
-Madi
