Re swelling plastics. Salt impregnated plastics will swell when submerged
long enough to become water saturated. There was a report some time back
that said they would become 12 times their size, but that has been proven
by several tests (including my own) to be a fallacy. It IS possible for
super-heavily salted baits to swell to nearly double their size though.
(the more salt to dissolve, the more they will swell). Even with more than
8 months of immersion in a test tank, I've never had any quite reach twice
their size.

I would offer a hypothesis that this situation (I hesitate to label it a
problem) is more commonly encountered today because there are more anglers
throwing heavily salted baits. First, they break off the hook on the cast,
hookset or during the battle far more often than traditional plastics, and
2nd, they sink. So there are more chunks of plastic "roaming free" in the
fish's habitat now than when most plastics weren't salted or carried far
less salt. Old style plastics didn't end up in the water unless you broke
off or discarded them there. Senkos and their ilk end up there by accident
all the time. Even when traditional (ie floating) plastic baits were lost
or discarded, they would float and eventually end up against or on the
bank, instead of on the bottom. Fewer of them ere eaten.

As far as their appearing in trout stomachs, I would suspect that corn is a
bigger problem. Corn is commonly used ad bait and as chum in waters where
stocked trout are targeted. I've caught rainbows and browns so full of corn
kernels than they were grotesquely bloated, and they apparently can neither
digest nor easily pass it.

RichZ©
www.richz.com/fishing