Thousands of fish concentrated in open net pens produce tons of feces. Combined with uneaten food pellets, this waste impacts the local environment, polluting the water and smothering plants and animals on the seafloor. Scientists are also concerned about spreading disease and parasites—common occurrences in crowded pens—to wild fish.
Where salmon farms are located near the migration routes of young wild salmon, parasites may infect and kill up to 80 percent of the wild fish. Pesticides and antibiotics used to control diseases and parasites can also leak into the environment, impacting local species.
Issue: Chemical Use
Many types of aquaculture require chemical treatments for a successful harvest. The amount of active chemicals released into the environment determines their effect on other organisms and human health. Frequent application and the emergence of antibiotic-resistant bacteria can reduce effectiveness and affect our ability to treat human diseases.
Containing the Problem
Onshore, "closed" farms contain wastes and other byproducts, making them easier to handle. U.S. fish farmers are experimenting with enclosed, recirculating systems, which filter wastewater and compost solid wastes to reduce the impact of untreated wastes. These farms can be located away from sensitive habitats where fish feed and breed.
Tilapia, catfish, cobia and trout are raised inland in the U.S. Most Arctic char is also raised onshore using systems that recirculate water, reducing disease transfer and pollution. All of these fish are delicious alternatives to ocean-farmed species and prove that most any fish—even salmon—can be farmed far from sensitive marine habitats.
By encouraging measures that protect our waterways and surrounding habitats, you're helping ensure that aquaculture is conducted in a sustainable way.
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Seafood Watch pocket guides help you select seafood that is caught or farmed in ways that help promote healthy oceans. Choose from the green, "Best Choice" column. Otherwise, try a yellow "Good Alternative."
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