Creative Solutions to Net Pens

What Are Net Pens?

Five circular net pens floating in the water, surrounded by boats and buoys, with mountains in the background.

Grieg Seafood British Columbia

Net pens are large cages suspended in bays along the coast or in large lakes. The pens can hold thousands of fish. They allow the fish to grow in a natural environment with the right water conditions.

Most fish farms in Canada use net pens. They are efficient, and produce fish at a low cost.

The Challenges

Net pens carry some risks, given that the only barrier between farmed fish and the environment is a net. These risks are greater on the East and West Coasts, where wild salmon populations are in decline.

  • The pens can be damaged during storms, allowing fish to escape. Fish that escape compete with wild fish for habitat and food. On the East Coast, they can even breed with wild Atlantic salmon.
  • The large number of fish in the pens attract sea lice, a common salmon parasite.
  • There is a risk of exchanging diseases between farmed and wild fish.
  • Fish poop and food accumulate under the net. This excess accumulation can cause pollution.

Creative Solutions

Fish farmers and researchers are coming up with creative ways to make net pens more sustainable. Here are a few examples.

Large blue and red ship floating in front of a coast, with two cranes and machinery on its decks.

This vessel has a freshwater bath in its hold in which to immerse the salmon. The freshwater does not harm the fish, but it does cause the sea lice to fall off their hosts.

Teal and white boat with beams and machinery extending out from the boat, floating on the water in front of a wooded shoreline.

Neptune Marine

This barge uses water pressure to remove sea lice and their eggs from salmon.

Illustration of a cylindrical net pen, separated into sections by nets, with fish swimming around lights in the lower part of the pen.

AKVA group

In this special pen, a net keeps the salmon deep in the water, where there are fewer sea lice.

Drawing of a net pen, with a cone-shaped structure suspended near the bottom of the pen, surrounded by food and fish.

AKVA group

By distributing feed deep in the water, farmers can encourage the salmon to swim below the level where sea lice are found.

Rather than managing sea lice alone, West Coast salmon farmers are now required to share information with each other about lice levels on their farms. This allows them to coordinate their efforts to control the parasite.

Research is underway to design an enclosure that would collect and remove salmon poop and excess feed.

View from a walkway surrounding a square net pen, with mountains in the background.

British Columbia Salmon Farmers Association

This sturdy net has a strong anchoring system that makes it more resistant to storms.

Lumpfish swimming through water, with a black hump along its back, and a white belly.

Natalia Sidorova/Shutterstock

These tiny lumpfish are hungry for sea lice. As they feast on the lice attached to salmon, they help control the parasite.

Two workers standing on the edge of a round net pen, making adjustments to the metal rim and plastic lining.

British Columbia Salmon Farmers Association

These floating closed pens will separate farmed fish from the surrounding environment.

Man sitting in front of an array computer monitors, showing underwater and surface views of a net-pen fish farm.

British Columbia Salmon Farmers Association

Farmers use cameras and artificial intelligence to monitor fish and supply just the right amount of feed.