Aquaponics, the combination of freshwater fish aquaculture and hydroponic vegetable production, is a practice I’m very familiar with. While living and working in the Bahamas, I helped design and build an expansion of the existing aquaponics system, and then ran the operation, providing the Island School with fresh lettuce every day and an occasional fish harvest.
There, I raised Nile tilapia (Oreochromis niloticus) in several fiberglass tanks that were connected to the hydroponic raceways by PVC pipes and a gravity-draining system. The water was recirculated via only one pump, which was located in the sump underneath the beds of lettuce. Water lost to evaporation was added automatically (thanks to the float-valve), and that water came from rainwater that had been collected and stored in cisterns under the buildings. The energy that kept the pump pumping came from a large solar array. So all in all, it was an extremely sustainable system! We originally had to import the tilapia fingerlings, but then started raising our own – something I learned by trial and error, but eventually I was successful in creating a self-sustaining system. Almost. The weakest link, the one I hated to admit: we still imported our fish feed from Cargill feeds.
Which is something that nearly all tilapia aquaculture operators in El Salvador do as well. In El Salvador, tilapia is raised three ways: extensively, in earthen ponds or small reservoirs with low stocking densities; intensively in aerated ponds or artificial raceways; or in cages located in ponds in a semi-intensive manner. But all three systems rely on the importation of feed. In one of the many imbalances of global food systems, El Salvador imports 2,415 tonnes of concentrated high-protein feed for tilapia production, yet exports only 230 tonnes (less than half of total domestic production) of tilapia, primarily to the U.S. And tilapia are fish with some of the highest feed conversion ratios!
Tilapia were introduced to El Salvador in the 1960’s, thanks to a program funded by the UN Food and Agriculture Organization (FAO). Yields per hectare (area being farmed with fish) vary from 1.5 to 10 tonnes per hectare, depending on how intensive the operation is. Aquaculture (which is nearly split evenly between tilapia and shrimp) as a whole is considered an insignificant part of the national economy (less than 1% GDP), and employs just over 1,000 people if you include the marketing, processing and distribution chains. The major problems that affect tilapia aquaculture are water quality issues, land costs, feed costs, diseases that plague the fish, and other environmental threats such as earthquakes, hurricanes, and pollution. However, tilapia production has increased dramatically since 2001, jumping from 28.8 tonnes to 654 tonnes, while marine shrimp and fish production has declined considerably.
But where are the plants? Well, primarily they are not there, which means that the fish are being raised in either earthen ponds or tanks without this extra benefit. If they’re in ponds, the density must be kept very low, unless the operators are pumping out and replacing water. If the fish are in tanks, the water must be aerated and replaced completely every day to prevent the dissolved oxygen (DO) from plummeting (thereby killing all the fish), and to remove the excess nutrient build-up (from the fish excrement and uneaten food). In an aquaponics system, the plants happily suck out these nutrients, and so the “clean” water is sent back into the fish tanks (which are still aerated).
Small scale aquaponics systems are cropping up here and there. Recently, Peace Corps volunteers built a small aquaponics system in El Triunfo, training local families in its simple operation. The hope is that the families will spread the knowledge of how to build and run the systems to other local families, to improve food security and self-reliance in that poor community. I am interested to find out if it is still in operation. But as far as large-scale operations, that remains to be seen. Because of my background in aquaponics, an investor contacted me for assistance in setting up a commercial-scale system in El Salvador. I’ve been communicating via email, and his operation is currently in the works. He has the tilapia fingerling growing in four large circular tanks and construction will be done on the hydroponic raceways sometime next month. He plans to sell his fish and vegetables to only local markets, such as local restaurants, food markets, and even grocery stores. His operation is located near La Libertad, which is a large beach town about a half an hour from the city. He feels he is far enough inland to not worry about saltwater problems, though he is concerned about the heat. Hot temperatures also cause the DO to drop to unsafe levels, harming not just the fish, but also the plants. If the DO is too low in the plant raceways, the plants cannot absorb the nutrients, which means not only is the water not getting cleaned for the fish, but that the plants are being deprived of those vital nutrients.
Overall, aquaponics is an excellent system, and is receiving a lot more notice these days, particularly in the States thanks to primarily one man, Will Allen (named last year as one of the 100 most influential people by TIME magazine) and his organization, Growing Power. Aquaponics certainly is not a new thing, but it’s becoming more popular because it is (or can be) a more sustainable way to raise both protein and vegetables, and can be done on tiny backyard scales, or profitable large commercial systems (see Bioshelters). I will be visiting what will soon be El Salvador’s first commercial aquaponics system in November, so I’ll post an update when I do. But for now, try to see if there’s any aquaponics near you!