New advances in water filtration and circulation make it possible for indoor fish farms to grow dramatically in size and production.
On a projection screen in front of a crowded home in a coastal Maine town, a computer-animated salmon swims swiftly through a huge oval tank. also, make it easier to remove dead fish, the narrator adds cheerfully.
The video is part of a launch earlier this year for an ambitious $500 million salmon farm that Norwegian company Nordic Aquafarms plans to build in Belfast, Maine, complete with what Nordic says will be one of the aquaculture tanks. biggest in the world. It’s one of a handful of projects in the works by Seafood Market hoping these highly mechanized systems will change the face of fish farming by moving it indoors.
If it catches on, indoor aquaculture could play a critical role in meeting the needs of a growing human population, says Nordic CEO Erik Heim. He believes it could do so without the pollution and other potential threats to wild fish that can accompany traditional aquaculture, although the inland approach faces its own environmental challenges. “There is always some risk, but the risk to the terrestrial system is a few percent of the risk to an outdoor system,” says Michael Timmons, an environmental engineer at Cornell University who has studied aquaculture for more than 20 years and is not involved. . . in the Nordic project.
Fish farming has often been touted as an extremely efficient way of producing animal protein: the Global Aquaculture Alliance claims that 100 kilograms of fish feed can provide up to 15 times more meat than an equivalent amount fed to cows. The industry has gained international traction, with farmed fish overtaking wild-caught (pdf) in the global food supply in 2014. But traditional fish farming methods have significant environmental drawbacks. For example, salmon farmers in Norway and Chile, the world leaders in salmon production, often use open-ocean cages that corral the fish in suspended nets or pens. This setup allows waste to flow directly into the environment, along with pathogens and parasites that can infect wild populations. Open-air pond farms, which are found around the world and represent the most common type of aquaculture in China, the world’s leading producer of farmed fish, also have a history of polluting local waterways with fish effluent. . and veterinary drugs used to keep diseases at bay.
Timmons argues that terrestrial interior systems can greatly reduce such risks. They isolate the fish from the environment and remove most of the waste from the water using recirculating aquaculture systems (RAS), which are similar to the filtration systems in a home fish tank, he says. But to date, indoor RAS farms have accounted for only a small fraction of the Seafood Market and are much smaller than Nordic’s planned operation. For example, Blue Ridge Aquaculture, the world’s largest RAS tilapia farm, located in Virginia, produces less than 10 percent of the amount of fish that Nordic expects to produce in Maine.
This recirculating technology has been around in some form since the 1970s but has evolved enough in recent years that Monterey Bay Aquarium’s Seafood Watch now ranks RAS-farmed fish as one of the available options for the most sustainable fish and shellfish. So “the natural thing to do is expand,” Heim told Maine residents during his recent presentation. The Belfast operation would include 18 of what Heim says would be among the world’s largest aquaculture tanks, every three times the volume of an Olympic-sized swimming pool, ultimately producing 33,000 tonnes of fish or about 8 percent of the US consumption, each year. . The company plans to build a similar farm in Norway next year that would contain the same size tanks, he says.
Although there are questions about whether the expansion increases the environmental risk of such a system, some experts believe the technology can make a sustainable transition in a big way. Community members at Heim’s hearing raised concerns about how the sewage could affect nearby coastal waters, but Timmons says the small amount of water discharged from RAS systems (from tank overflow and tailings from the cleaning sprayed from the filters) is often cleaner than when it enters. The water in RAS tanks flows through a bubbling container called a biofilter, in which bacteria consume the fish’s urine and convert it into a form of nitrogen that is safe for the fish and the environment, says Michael Schwarz, director of Virginia Seafood Agricultural Research. and Extension Center. Physical filters collect fish faeces and food scraps that can be stored and resold as compost or biogas feedstock. Ozone treatment helps break down foamy organic solids and ultraviolet light is used to kill pathogens.
