Mud snails do not help the situation, but you also have siltation and weed beds reducing or changing insect habitat. The greatest problem associated with siltation is the potential reduction in suitable spawning habitat that the fish need to reproduce. Tack on illegal fishing and predators such as otters and cormorants, the wild fish are facing a perfect storm of "bad" factors affecting their survival and population expansion. Since you been away a few years, you may not know that Putah Creek Trout is assisting DFG in evaluating the wild trout population, with a goal of designating the 4.5 miles of Creek as a wild trout water.

Freeze your gear overnight or put in a closed black plastic bag in the sun for 1 hour. Former technique is easier on waders and shoes. 409 degreaser was the early on recommendation, but is hard on rubber and plastic and has to be disposed of. Carefully rinse and inspect your wading gear afterward, recommend driveway or other hard surface that does not drain into sewer system for rinse.

The mudsnails do not come from larvea, they are live bearing and the juvenile are almost microscopic. The reason these things can survive so well out of water is the have a periculum or a "trap door" that they close when they sense danger. They can even survive being eaten by fish.

Introducing non-native agents for control is fraught with problems and nonspecific poisons are not going into drinking water. Unfortunately little data has been collected on the damage of the snails to this ecosystem, but it doesn't seem to be destroying it, or even doing much overall damage. IMV a bigger problem is siltation which is definitely affecting the fishery.