When large numbers of fish or shrimp are kept in pens or ponds, some can escape. This isn't as harmless as you might think. For instance, when Atlantic salmon escape into the waters of the Pacific, they compete with already threatened wild Pacific salmon for food and disrupt habitat in wild rivers and streams.
Most farmed species are not the same as wild species in the area, and no one knows the implications of these introductions. Escapees can potentially breed with wild species, causing genetic changes and the possible extinction of certain populations. They can also establish themselves as invasive species, as is the case with tilapia raised outside Africa.
As long as salmon farmers and others continue to rely on open net pens, escapes will continue to threaten wild populations of salmon or other species, and natural habitats.
Seafood Watch pocket guides help you select seafood that is caught or farmed in ways that help promote healthy oceans. Choose from the green, "Best Choice" column. Otherwise, try a yellow "Good Alternative."
Download or print a pocket guide