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Steelhead

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Ocean Wise Recommended

Ocean Wise

Variety

Steelhead

Oncorhynchus mykiss

Method

Farmed

Recirculating Aquaculture Systems (RAS)

Location

Worldwide

Overall Rating

6.7 / 10

Summary

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.

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Ocean Wise Recommended

Ocean Wise

Variety

Rainbow trout, steelhead

Oncorhynchus mykiss

Method

Farmed

Open net pen

Location

US

Overall Rating

6.71 / 10

Summary

Rainbow trout are native throughout many freshwater systems of North America and have also been introduced as sport fish. The US produces 15,000 mt of rainbow trout and is the 10th largest producer in the world. The majority of the aquaculture operation occurs in raceways, but 3,600mt is produced in net pens from a single farm in the Columbia River, Washington.

The nature of open net pens allows for effluent containing excess feed and fish waste to flow directly into the environment. However, the habitat surrounding the farm is strictly monitored, and has not been observed to have been significantly affected. Cumulative impacts of numerous farms in one area are minimized due to strict regulation which limits the size of the industry. Although few chemicals are used, the open net pens allow the chemicals to be discharged into the surrounding water.

Rainbow trout are sourced from domesticated broodstock. This relieves fishing pressure on wild populations of rainbow trout. However, rainbow trout aquaculture uses wild fish resources in the form of feed. Rainbow trout are carnivorous fish which require about 1.5lbs of fish in the form of feed for every 1lb which they produce. They are raised with a net loss of protein.

The risk of escapes in open net pen systems is high. However, since the farmed rainbow trout are sterile, they cannot breed and genetically compromise wild populations. Furthermore, hatchery-raised rainbow trout are intentionally stocked in the wild for sports fishing. Therefore any escapes would not significantly change the present ecosystem. Open net pens can cause transfer of disease from farmed fish to wild populations. In the case of rainbow trout in the US, vaccines and effective husbandry and management greatly reduce this risk.

Data quality and understanding of rainbow trout operations in the US is high. Scientific literature, industry data and government information is also readily available. Management limits the size of the industry in order to minimize cumulative environmental impacts of numerous farms.

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