Humans consume more than 100 million tons of fish per year, and nearly half of that is farmed fish. In some ways farming is good; we’ve been overfishing many species in the wild. But aquaculture facilities also bring a host of problems. In some places, coastal wetlands and mangrove forests have been destroyed to make way for fish farms. They can also pollute the near-shore environment. The shallow, still water and concentrated excrement from fish provides an ideal breeding ground for sea lice; salmon are particularly vulnerable to the parasites.
New technology is allowing a different kind of fish farming. Massive frames, more than 100 meters in diameter and about 68 meters high, are submerged several miles offshore and stocked with young fish. The structures are exposed to strong ocean currents that keep their water cleaner and better oxygenated than that of farms nearer to the coastline. The cages can be equipped with all sorts of equipment, such as cameras and oxygen sensors, as well as feeding tubes that can be placed at different depths. Rather than sprinkling food on the surface of the water as you might do in a fish tank—and as near-shore farms usually do—the feeding tubes force the fish to swim deeper to feed, which kills most of the sea lice.
Smaller open-ocean “aquaculture nets” are already deployed at various places throughout the world, but these large structures—each with a volume greater than that of St. Peter’s Basilica, as this article points out—are on a different scale entirely. Each can house up to a million and a half salmon. Norway is acquiring six of them in an attempt to triple its farmed fish production by 2030.
Have you had experience with aquaculture in your area—in particular, has it either degraded water quality, or itself been affected by pollutants in stormwater runoff?