I had the oppurtunity to visit alot of different waters on my recent eastern sierra trip and everywhere you go mudsnail warnings are posted and most waters seem to be mudsnail positive. The hot creek hatchery even has a huge sighn that reads absolutly no waders, or hip boots aloud on the premises, took me a bit of thinking of why this was posted. What long term effects are these critters going to have on our fisheries ?
If mudsnails become more of a problem then they already are I can really imagine a time in the not to far future were it will be illegal to wade in certain waters. That would not be good.
One very strong reason is that if snails are introduced into the hatchery, the fish there can be "carriers" to other waters when they are planted. The snails can survive in the fish's digestive tract and be passed alive into new waters. There is a big concern that the AR snails do not get into the Nimbus hatchery; if they do the fish will go to already contaminated waters like Putah.