Rubber worms ingested by fish

I saw a couple years ago that Maine was considering a ban on soft plastics under the premise that fish were being harmed by ingesting either lost, broken or discarded worms. Personally, I have caught large landlocked salmon and several brook trout in the Adirondacks with rubber worms in either their stomachs or intestines that were not attached to hooks. Anyone else experience this? Does anyone know of reliable studies on fish mortality from soft plastic ingestion?