Ecological Aquaculture

Ecological aquaculture, or “integrated multitrophic aquaculture,” involves designing farms to function more like healthy aquatic ecosystems. Generally, fish farms produce waste and pollute surrounding waters because of the high concentration and limited mobility of the fish. These factors also leave the fish more susceptible to disease. However, farms that integrate complementary species can greatly reduce pollution and disease levels. Cooke Aquaculture’s salmon farm in Back Bay, Canada, takes advantage of a natural ecosystem cleansing service provided by blue mussels and kelp. The shellfish filter excess waste from the fish cages, while the seaweed thrives on dissolved nutrients in the water.

Farming in the Warehouse

At the Center for Marine Biotechnology in Baltimore, Maryland, researchers are using city-supplied water and a complex filtration system to raise a few hundred fish completely indoors. Raising fish in a closed pen, either in a warehouse or floating on the ocean, avoids the common pitfalls of modern fish farming: net pens pollute coastal environments with waste and antibiotics, fish escapes threaten the diversity of wild populations, and diseases can spread easily. The Center’s operation is the first indoor marine aquaculture system that can re-circulate nearly all of its water and expel zero waste.

Cleaning Wastewater

If managed correctly, fish farms can go beyond addressing the problems caused by the industry itself and provide a net positive impact on the environment. Traditional ponds outside of Calcutta, India, called bheris, produce some 13,000 tons of fish a year for the city’s 12 million inhabitants, and serve as critical bird habitat. But the bigger environmental service they provide is that the fish feed on the 600 million liters of raw sewage that spews from Calcutta daily, turning a health risk into a key urban crop.

Restoring Habitats

Fish farming can help to restore degraded coral reefs and wetlands. The metal cages that hold farmed shellfish often function as artificial reefs around which striped bass, shad, and other marine species congregate. In the Caribbean, the Caicos Conch Farm raises King conch not just to sell to restaurants around the world, but to help re-seed coral reefs with this keystone species.

Eating Local Seafood

People who eat from their local waters have a natural reason to be concerned about what goes into them. The Southold Program in Aquaculture Training (SPAT) on Long Island, New York, helps volunteers raise baby shellfish in floating cages to restore the local scallop economy. Participants receive training in algae growth, marine ecology, and shellfish dynamics, and also get to eat half their harvest of fresh, mature shellfish. In turn, they report changing their daily habits that affect water quality, such as shunning chemical fertilizers, upgrading home septic systems, and using nontoxic paint on their boats.

Eating Little Fish to Save Big Ones

In Peru, massive schools of the tiny Peruvian anchovy are netted each year. Although the fish is chock-full of the same beneficial fatty acids that have made tuna, salmon, and other big fish famous for warding off heart disease and boosting brain development, nearly all of the anchovy catch is turned into fishmeal and fish oil, used to fatten pigs and chickens on factory farms worldwide. To address this problem, students at the University of Lima have launched a campaign to change the image of the anchoveta from something that only poor people eat into a tasty dish for well-heeled sophisticates.