Open-net farms in Chile (Credit: C Peet)

Every year, millions of fish escape from aquaculture facilities worldwide. Fish farming systems need to be able to keep their stocks under control. Open net-pen systems and shrimp ponds are the most vulnerable to escapes.

Ecosystem Gate-Crashers

Little is understood of the potential full implications of escaped species. Escapees can inter-breed with wild stocks or compete with them for food, spawning habitat, and other resources. For the most part, farmed species are the same as the native wild species in the area. Farmed escapes may establish themselves as an invasive species.

As long as the aquaculture industry continues to rely on open net pens, escapes will continue to threaten wild populations of salmon or other species, as well as natural habitats.


  • Avoid open-net farmed salmon. Choose closed containment (Canada, U.S.) farmed salmon instead.
  • Avoid pond farmed shrimp. Choose closed containment (U.S.) farmed shrimp instead.
  • Choose closed containment farmed finfish: Arctic char, rainbow trout, barramundi (U.S.), tilapia (U.S.) and salmon (Canada, U.S.).
  • Understand the risks posed by GM salmon.


Closing the Problem

Open nets and coastal ponds are inherently vulnerable to escapes. For example, predators or rough weather can tear holes in net pens. Closed containment systems eliminate escapes.