Aquaculture—the farming of marine organisms, including fish, shellfish, turtles, and plants—is responsible for more than half of all seafood eaten worldwide, and getting bigger. It’s widely seen as the most efficient way to provide protein to the rapidly growing global population, slated to reach over 10 billion people by 2050. The rapid growth in global aquaculture production has created questions of long-term sustainability in aquaculture.
Falk School Aquatic Lab Director Roy Weitzell, PhD is ready.
The Lab is loud. Not factory-loud, but it’s abundantly clear that things are happening. As befits Eden Hall Campus, these things are powered entirely by energy generated on campus. Water is cooled or heated on demand using the geothermal heating system, electricity is generated by solar panels, and Roy hopes to eventually use Eden Hall crops to make fish pellets. Perhaps most impressively, between 98 and 99 percent of the 5000 or so gallons of water is recycled in a continual process of filtering within the Lab (the other one to two percent is used to water plants across campus or treated in the campus sanitation system and re-infiltrated into the local aquifer).
“It’s a great example of how all these sustainable systems can come together and support serious infrastructure in a relatively small space,” says Roy. The lab is divided into three main parts: fish tanks, aquaponics and research stacks.
The space is dominated by three large, round fish tanks holding a total of about 1500 gallons of water. Combined, they’re able to hold around 850-1000 foot-long rainbow trout. Having three tanks allows Roy and his students to research how fish-related variables (e.g., coloration, taste, texture, size, and growth rate) are affected by environmental variables (e.g., insect-based vs. plant-based fish food, amount fed, and water source). Roy notes that the lab is able to culture a range of cold-water and warm-water species.
Fish from the tanks will also be used by Eden Hall Chef Chris Galarza and his team to create meals for the EHC community and special products, such as a “signature smoked trout spread.” Roy also looks forward to working with the Falk School’s Food Studies Department, mentioning an Asian fish paste as a possible initiative that the Lab could help support.
Aquaponics—a portmanteau made from aquaculture and hydroponics—refers to the mutually beneficial growing of fish and plants together in one physically interconnected system. Here’s how it works:
- Waste is collected from the fish tank, and pumped to the growing beds.
- Bacteria in the growing beds transform ammonia from the waste into nitrate, which makes an ideal plant fertilizer.
- Plants filter nutrients (nitrate and macronutrients) from the water, and the water is returned to the tank.
“Aquaponics has a lot of backyard hobbyists. It’s very easy to do, cost-effective, and there are a lot of resources to help,” Roy says, mentioning Pittsburgh Aquaponics as one of them. Chatham’s system was built by four students in the Falk School’s Agroecology and Sustainable Aquaculture classes.
In the growing beds, plants are embedded in a bed of expanded clay pellets. “We use these because they’re very light, easy to work with, and the porous surface provides more space for bacteria to grow,” notes Roy. Come fall, students will be using the system to grow collard greens (also chard, peppers, tomatoes, basil, etc.).
Roy estimates that the aquaponics system will be able to grow 40 tilapias from one to two inches to “plate size” in four to five months. “But that’s part of the grand experiment,” he says. “We’ll be adjusting variables to see where we get the best results.”
You’re basically recreating what nature does on its own, but could never do it at this density. Growing a lot of fish in a small space lets us feed more people.”
Eventually, Roy hopes to add insects and worms to the food they feed the fish. “They’re nutritionally dense, and their larvae are an ideal food source,” he says, adding that worms in the growing beds can also help break down organic material.
Toward the back of the Lab are the “research stacks” – aisles of many small tanks stacked together (“sort of like a fish condominium,” Roy says) with a recirculating system. At the moment they’re mostly empty, but Roy plans to use them to grow and display aquatic life, such as native fishes and aquatic invertebrates. “The life cycle of fathead minnows is the perfect fit for the teaching semester,” he says, explaining that they grow from an egg to a reproducing adult in only three to four months. Roy is also interested in using the stacks to expose students to other such forms of local aquatic life, such as salamanders and fresh water shrimp. The large number of tanks allow a degree of statistical rigor that lets us expand our findings to the outside world.
This is first and foremost a teaching laboratory,” Roy says. “Education comes first; research is second.”
That’s not to say some pretty fascinating research isn’t in the cards. Inside fish ears are tiny structures called otoliths. As fish age, the otoliths lay down bands, much like rings inside tree trunks. Like rings of a tree trunk, these bands can be “read.” They can be used to determine not only the age of the fish, but also potentially abrupt chemical changes in the fish’s environment, and together with Duquesne University’s Brady Porter, PhD, that’s what Roy is interested in exploring. The plan is to start by breeding minnows in the research stacks, to minimize variables. Once the minnows are grown, they’ll be exposed to salt compounds, such as road salt, fracking brine, and acid mine drainage. The researchers anticipate that this exposure will produce telltale otolith rings that can then be used to help identify toxicity in rivers and streams.
In Spring 2017, Roy will be teaching Sustainable Aquaculture for the Falk School of Sustainability.
 FAO 2012. The State of the World’s Fisheries and Aquaculture. United Nations Food and Agriculture Department