Illustration of Steelhead



Seafood Variety

Harvest Method


Ocean Wise Recommended

Ocean Wise



Oncorhynchus mykiss



Recirculating Aquaculture Systems (RAS)



Overall Rating

6.7 / 10


Recirculating aquaculture systems (RAS) are similar for various farmed species. This recommendation applies to all species grown in RAS except for those where a separate species-specific RAS recommendation is available. Closed containment has recently emerged in the farming industry as an alternative to net pens in order to reduce the environmental impacts of an aquaculture system that is open to the environment.

Source of stock is domesticated broodstock for the vast majority of RAS farms. Therefore wild populations are not depleted to source the aquaculture operations. Impacts of feed use vary amongst RAS farms and the species being cultured.

The contained nature of RAS allows for close control and prevention of potential disease or parasite outbreaks. Risk of pathogens and their transfer to wild populations is low. Predator and wildlife mortalities are virtually eliminated when RAS systems are located indoors, and risk of escapes is low as the systems are not in direct contact with natural water bodies.

About 90-99% of water is typically recirculated after filtration and waste treatment. As such, little to no effluent is discharged to the environment and there is the opportunity to treat waste before discharge. The closed design of RAS and the application of biosecurity protocols reduce the risk of disease and parasites, and consequently require low use of chemicals. When chemicals are used, they cannot flow into the environment directly, and have the opportunity to be treated and sterilized before discharge. RAS farms are typically not built in sensitive habitats, and the closed system of the farms minimizes ecosystem impacts.

Learn more about harvest methods