What’s at Stake
As the ocean warms, it affects wild fish and fish raised in ocean pen farms. Coldwater fish such as trout are less likely to survive in warmer water due to trouble breathing. Some fish, such as salmon, even develop bone deformities when raised in warm water. Many wild fish populations are simply moving further north, but what happens to the fishing jobs left behind? And how will we raise enough marine fish to meet consumer demand? The answer could be indoor fish farms.
Recirculating aquaculture systems (RAS) are indoor fish farms that use tanks to raise fish on land. RAS farms allow farmers to control the water temperature. They produce much less water pollution than ocean net-pen farms because they filter the water. Even when there are marine heatwaves, indoor aquaculture farms keep their cool.
RAS farms clean and monitor the water to keep fish healthy, so the fish survival rate is high. Because the water is filtered, RAS fish are less likely to contain pollutants such as microplastics that fish ingest in the wild.
Advantages Over Ocean Net-Pen Farms
In terms of marine heatwaves, the most obvious downside of ocean net-pen farms is that they can’t control the water temperature of the ocean. In terms of disease, ocean net-pen farms are notorious for spreading disease and parasites, such as fish lice, to wild fish. Ocean net-pen farms also release more pollution into the sea. The fish poop leaving ocean net-pen farms is not filtered or processed, unlike the waste from RAS farms. Because the waste is hidden under the water, many people don’t realize how much ocean net-pen farms pollute.
Some Downsides to RAS
RAS farms require a larger up-front investment than ocean pen farms. That investment may put RAS farms out of the reach of developing countries—or most people in the fishing industry in the U.S. A shift from wild-caught to aquaculture will mean less independence, less entrepreneurship, and more reliance on large corporations for jobs. On the other hand, RAS facilities create jobs and add to the tax base in their communities.
RAS farms are a source of public concern about pollution, even though they’re cleaner than ocean net-pen farms. Because their outflow pipes run into the ocean or local waterways, RAS farms sometimes face public opposition. For example, Nordic Aquafarms has been trying for several years to get permits to build a $500 million RAS farm in Belfast, Maine. The farm would raise 66 million pounds of salmon annually.
The company is faring better in Humboldt, California, where they are currently in the engineering and permitting phase. In California, Nordic Aquafarms has agreed to pursue a full environmental impact report, going above and beyond California’s Environmental Quality Act.
Of course, the best solution would be to slow climate change so wild fish stop leaving current fishing grounds. However, RAS farms may be our best option for raising clean, healthy, sustainable fish if that’s not possible.