Concentrated fish can mean concentrated waste. Combined with uneaten food pellets, fish waste can impact the local environment by polluting the water and smothering plants and animals on the seafloor. There are also concerns that diseases and parasites—common occurrences in crowded pens—are spread to wild fish.
When Farmed Meets Wild
When net pens are located near the migration routes of wild fish populations, there is the potential for on-farm diseases to be transmitted to passing wild fish. Pesticides and antibiotics used to control diseases and parasites can also be discharged 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 can reduce treatment effectiveness and the emergence of antibiotic-resistant bacteria can affect our ability to treat human diseases.
Containing the Problem
Onshore, “closed” farms contain wastes and other byproducts, making them easier to treat. U.S. fish farmers are experimenting with recirculating systems, which filter wastewater to reduce their impact on the surrounding ecosystem. These farms can also be located away from sensitive habitats where fish feed and spawn.
Tilapia, catfish, cobia, Arctic char and trout are several examples of species raised in onshore systems throughout the U.S. All of these fish are delicious alternatives to some poor-performing, ocean-farmed species and are proof that most any fish can be farmed with little or no impact to sensitive marine habitats.