Aquaculture Methods

Aquaculture or ‘fish farming’ may take place in the ocean or on land, and can be used to grow marine or freshwater species. The environmental impact of farmed seafood is to a great extent  determined by the  farming method used. Here is a summary of common aquaculture methods.

AquaSeed – Closing the loop on farmed salmon. Click here for the SweetSpring Salmon Profile.

open-net-pensOpen-net pen systems

Found offshore in coastal areas or in freshwater lakes, open-net pens or ‘cages’ are considered a high-risk aquaculture method as they allow for free and unregulated exchange between the farm and the surrounding environment. Farmed salmon are typically farmed in this manner. Open net pens allow free exchange of high concentrations of waste, chemicals, parasites and disease. Farmed fish can escape and they also attract predators, such as marine mammals, that can get tangled and drown in fish farm nets.


Closed Systems: Closed systems or ‘closed containment’ farming methods use a barrier to control the exchange between farms and the natural environment. This significantly reduces pollution, fish escapes, negative wildlife interactions, and parasite and disease transfer from farms to marine and freshwater ecosystems. Follow link for information about Kuterra salmon.

closed-systemsRaceways: Flowing water is diverted from natural streams or a well. Raceways are typically used for raising rainbow trout. To be considered a low-risk method, waste must be treated and fish escapes prevented.






recirculation-systemsRecirculation systems: Water in these systems is treated and re-circulated. Almost any type of finfish can be raised in recirculating systems. Common species farmed in this manner include Arctic char, striped bass, barramundi, sturgeon, and increasingly salmon. This system does not mix with natural water sources, which mitigates pollution, parasite transfer and fish escapes.




pondsPonds: Ponds are semi- or fully enclosed body of water. Catfish, tilapia and shrimp are typically farmed in this manner. Discharged waste must be filtered and treated to be considered a “low-risk” method. “High-risk” pond farms discharge untreated wastewater which pollutes the surrounding environment. They can also cause devastating habitat destruction. For example, the construction of shrimp ponds in Asia and South America has (note: subject here is “construction”, noun, singular!!!) destroyed 3.7 million acres of mangrove forests along the coast.



SOLUTIONS for “High-Risk” ponds – Closed Containment


Farmers grow shellfish on beaches or suspend them in water by ropes, plastic trays or mesh bags. The shellfish farmed using these methods are filter feeders and require only clean water to thrive. Oysters, mussels and clams are cultured using suspension systems. Shellfish farming with suspended-aquaculture is often ‘low risk’ if the farmed species is native to the area and if the farm has sufficient flow to prevent waste accumulation.



  • Avoid open-net farmed salmon. Choose closed containment (Canada, U.S.) farmed salmon instead.
  • Avoid pond farmed shrimp. Choose closed containment (U.S.) farmed shrimp instead.
  • Choose farmed shellfish: oysters, clams, mussels and scallops.
  • Choose closed containment farmed finfish: Arctic char, rainbow trout, barramundi (U.S.), tilapia (U.S.) and salmon (Canada, U.S.).
Wildlife Refuges of the Seas Currently approximately only 1.17 per cent of our oceans are protected. The implementation of a network of Marine Protected Areas would ensure refuges for wildlife which could be otherwise threatened by development. Refuges also support commercial fisheries by serving as “productivity zones”. A Green Economy Times are a-changing. Retail markets and other major buyers are adopting Sustainable Seafood Policies. Innovations are being made in aquaculture technologies, such as closed containment and improvements to feed. A ‘green economy’ needs government support and industry buy-in. Sustainable aquaculture markets will thrive with government incentives and investment in greener technologies.