A Tour of the Cuerci Fish Farm

By Geoffrey Nathan

After completing our stay at the Palo Verde biological station located in the dry Guanacaste region of Costa Rica, our group arrived at our designated Cuerci station set in the heart of the Talamanca mountain ranges. We found ourselves situated in a gorgeous rustic area, with nothing but hills, grass, and the occasional scattering of small homes as far as the eye could see. Our new home was a snug cabin. It was built entirely out of wood, had stoves and fire pits, and most importantly we were told that delicious hot chocolate was served during the evenings when the temperature dropped.

After getting settled in by finding our rooms, having some lunch, and resting up a bit from our 5-hour bus trip, we were introduced to the owner of the cabin, Carlos, and an accompanied researcher, Miguel, who would be staying with us during our visit to Cuerci. Shortly after laying out the cabin ground rules, Carlos took us on a short walk to his fish farm situated on the same property. I had never seen a family-owned fish farm before or had any prior knowledge into how a fish farm operated so I had no idea what to expect.

The fish farm had about 5 different ponds, all of them with a continual supply of freshwater being poured into them from a nearby river, some ponds larger than others. Carlos explained to us that the fish he farmed were rainbow trout, introduced 60 years ago from the US and Canada. Upon first glance you could see a few trout swimming around in the ponds. I estimated there to be about 50-100 trout per pond. However clearly I am very poor at estimating trout abundance, because it turned out that Carlos currently was raising about 10,000 trout. He explained to us that there are many methods he uses to increase trout production. He massages fish in certain ways to ensure that they lay their eggs and is able to pick out the eggs that will successfully fertilize based on color and size. He then grabs trout semen and mixes them with the eggs in a cup in order to fertilize the eggs.

Carlos then went on to explain how he attempts to increase the size of the trout. Interestingly this begins with receiving imported eggs that produce sterile females. As illogical as this sounded, Carlos explained that females unable to produce eggs grow bigger than those that do because energy allocated toward egg production stunts growth in these females. Another technique that Carlos uses to increase the size of the fish is to feed the fish boiled eggs at an early age. The yolk acts as a valuable energy source for the fish and provides them with the necessary nutrients for healthy growth.

By the end of the tour, I found myself very intrigued by the maintenance and tactics that went into running a fish farm as well as impressed by the dedication to maximum production that Carlos had for producing the best quality fish.