Net pens are a common way to farm fish such as salmon. Water flows freely into and out of the pens, and can carry untreated waste and chemicals into the surrounding environment. Farmed fish can escape and compete with wild fish for natural resources or interbreed with wild fish of the same species, compromising the wild population. Diseases and parasites can also spread to wild fish living near or swimming past net pens. Not all seafood farmed in net pens is bad, however. There are net pen farms