Aquaponics Curriculum Teaches New Fish Farming Techniques to Ag Students

Agriculture students at Sanger High School in Sanger, near Fresno, CA, are experimenting with new techniques of fish farming. These new techniques are very efficient, reduce environmental concerns and provide a flexible platform that can be scaled from a small system for home use to a large commercial operation. Called ‘aquaponics,’ the system combines aquaculture (fish farming) with hydroponics (growing plants without soil).

“This is a new field of agriculture, and I’m very excited to be studying something that is so cutting edge,” Audrey Bonomi, Department Chair of the Agriculture Program at Sanger Unified School District, said. “With the help of John Young and others, we’re developing equipment and techniques that may change how fish are grown for market in this country.”

Young, a Sanger area grower (J and J Aquafarms) who has been involved with aquaculture since the 1980s, is the technical advisor for the project. The project was set up as an ongoing experiment to obtain data on plant and fish development with different plant media, fish food, or types of plants grown.

“Aquaponics makes sense,” according to Young, “the fish waste is a rich resource for the plants, and using the water for the plants cleans and oxygenates the water for the fish. It’s an environmental balancing act that is mutually beneficial.”

Demand for fish, especially in the USA, is dramatically increasing but the supply of uncontaminated wild fish is shrinking just as dramatically. Some scientists estimate that as much as 70% of the world’s fish have been fully exploited or completely depleted, yet over 1 billion people rely on fish as their primary protein source.

With this collision of needs, fish farming is a booming new subset of agriculture. Aquaculture is one of the fastest growing segments of the US and global agricultural economies, growing at a rate of 6.5% per year, according to the Fisheries Technologies Associates, Inc.

The 2007 USDA census of agriculture counted 6,409 farmers and ranchers reporting freshwater aquaculture sales in the US. Total sales were $1,415 million. California reported 102.2 million of those sales, making it the 5th largest state in aquaculture sales (the top 4 were Mississippi, Washington, Arkansas, and Louisiana). The total US value of sales for freshwater aquaculture products increased 25 % since 2002, showing the explosive growth in the industry. Fish farms are being created not only on land, but in lakes and oceans around the world.

Saltwater as well as freshwater fish are now being farmed. It is a new industry fraught with challenges and pitfalls, but also great rewards.

“These days, when you buy fish at a market or in a restaurant, unless it is labeled as wild-caught, it came from a fish farm,” According to Young. “Wild-caught salmon, for example, is seasonal and costs substantially more than farmed salmon. Farmed salmon is a consistent, year-round, good-tasting product that fills a huge void.”

Some of the large fish farms built out on the oceans have been criticized for polluting waterways due to the large numbers of fish kept in small areas. Held in a network of cages or nets, the individual fish has much less space than they would have in the wild and the resulting accumulation of fish waste and unconsumed fish food can pollute the area around the farm.

Additionally, infections or diseases are treated with drugs or chemicals that are not normally found in the water.

According to a report published by the WorldWatch Institute, a poorly-run fish farm on the ocean could devastate wild fisheries. The report says a fish farm with 200,000 salmon would release about as much contamination as the raw sewage generated by as many as 60,000 people.

For the most part, fish farms located on the ocean have been loosely regulated, if at all, and reportedly, some are using chemicals that are banned in US fisheries and would otherwise not be allowed to enter the food chain in the US.

Efforts to regulate offshore fish farming have led to the formation of several private and governmental groups who are developing best practices guidelines. One such non-profit group, The Global Aquaculture Alliance, was formed to develop standards for seafood farming that address food safety, environmental, and product quality concerns. They now certify the companies who meet their BAP (Best Aquaculture Practices) standards. The group is striving for voluntary compliance by seafood farmers with verification by the Alliance.

Unlike the ocean fish farms, an aquaponics system is a

closed circuit – the water remains with the fish and vegetation. The water is cycled through the vegetation grow bed using an autosiphon system that allows the bed to fill with water, then drain so the root systems are not constantly in water. The fish waste contains substantial amounts of nutrients to feed the plants.

“This will work well with leafy plants, such as lettuce, which is what we planted in our first experimental beds,” according to Young. “But fruiting plants need additional nutrients. However, It may be that some or all of these needs can be met with changes in the fish food.”

The first two phases of the study at Sanger High School are complete, but much more lies ahead.

“Our first goal was to test our system and gain experience with the equipment,” Instructor Bonomi said. “Our Ag Mechanics teacher Greg Ravy designed the framework and his students modified the tanks. With John Young’s help we designed the plumbing and chose lava rocks as our first growth media.” Bonomi said other choices for media include gravel or styrofoam. “The fish we chose were Carp and Bluegill.” Ideally, the fish grow to frying-pan size before being harvested.

“Our first real experiment was to try different types of lettuce to determine growth rates and which would work best,” she continued. The students regularly recorded the growth of the lettuce and the fish, and monitored the water chemistry.

Not only did they gather good data about aquaponics plant and fish growth, Bonomi said their first crop was a complete success. “It was some of the best leaf lettuce I ever tasted, and the size and quality was terrific. One of the best things was, we had not one weed in the crop. We had some gnats in one area, and an occasional spider, but no other pest problems. We grew these totally organically, with no pesticides used at all.”

The next step is to grow a fruiting crop. Tomatoes have

been planted and the students will continue to measure and monitor the crop’s progress.

“With the aquaponics, my ultimate goal is to grow crops for 3 seasons – spring, summer, and winter. We want to put our crops in our own farm store that sells wholesome, organic vegetables. While we’re doing this, we are training our students for a future in agriculture.”

Bonomi sees aquaponics as an important segment of that future, with an ever-increasing share of the fresh food market.

“Even right now, it’s an efficient way to grow both fish and vegetables,” she said. “It’s going to get even better. The more we learn, the more efficient the process becomes. I’m sold that this is a cost-effective way to get our food on everyone’s table.”
Article and photos by Len Wilcox