POLLUTION & HABITAT | MARINE RESOURCES | RISK TO WILD STOCKS | MANAGEMENT | ECOLOGICAL EFFECTS
Risk of Pollution and Habitat Impacts
Rainbow trout farmed in the United States primarily comes from Idaho, where they tend to be raised in concrete raceways that are like artificial streams. These freshwater flow-through systems filter out waste products and discharge treated or partially treated water into streams and lakes nearby, according to the Blue Ocean Institute. The discharged water can contain an overabundance of nutrients that affect local water quality, producing more algae, according to the New England Aquarium. Regulations are in place to monitor water quality in the United States so this doesn’t become a problem.
Rainbow trout are also raised in floating cages in both salt and fresh water to larger sizes of 6 pounds and up. This fish is usually marketed as steelhead in North America and as "salmon-trout" in other countries. This method, which is found mainly in Norway and Chile, but also in the U.S. and Canada, is high-risk due to the increased likelihood of pollution getting into local waterways.
Use of Marine Resources (Feed)
Rainbow trout eat feed that contains a relatively large amount of fishmeal and fish oil. The Monterey Bay Aquarium points out that trout are fairly efficient at converting their feed into protein, though. Recent innovations in rainbow trout feed enable the fish to digest the food even more efficiently as well. University of Idaho researchers are trying to figure out a way to replace fishmeal and oil entirely with the byproducts of grain and ethanol production.
Risk to Wild Stocks
There is no evidence of rainbow trout escaping from farms in Idaho, where the majority of the fish is raised in the United States. Since the species is native to the Pacific Northwest, even if trout did escape, the impact in Idaho is likely to be minimal, the Institute added. In Colorado, where the fish are raised in ponds, there have been outbreaks of a pathogen that leads to a condition called Whirling disease, so the state regulates that trout farms there must be certified as being free from the disease.
Water quality regulations in the areas where trout are farmed in the U.S. are robust, and monitoring is consistently performed. In the United States, the Environmental Protection Agency manages effluent from trout farming operations. In addition, the Seafood Choices Alliance notes that Idaho has agencies that enforcing water quality limits at the state level.
Most rainbow trout farms in Idaho have protective netting that keeps birds away from the fish without harming them. Although most trout farms divert fresh, clean water from local waterways into raceways and farms, there is no evidence this depletes groundwater.