Fish poisoning may make way for Utah native trout

If the poison they are using is rotenone (the most common chemical used to remove non-native fish), it is a plant based poison that binds with oxygen in the water. Potassium permangenate is used to counteract the chemical at the bottom of the reach being treated, so it is limited to a small section of the river at a time and doesn't affect anything downstream. The rotenone only affects oxygen breathing organisms, like fish and some aquatic insects, and the treatments are usually timed to avoid killing amphibian larvae. It is safe for birds, mammals, etc. to drink water being treated. The concentrations used are usually low enough that it doesn't kill off all fish anyway, if they can find a trickle of water coming in from a side channel, they can hang out there and get enough oxygen to survive. This article would have been more informative if it had identified the chemical to be used and given some facts about it.

Why not make the area a no catch and no possession limit and let it be "fished out" instead of poisoning everything?