Gary,
Trout are really stupid when taking a bait,ye right,so when did a pike ever see a gurnard,herring,gosatfish swimming about in his territory,or barbel finding boilies under a roxk and bit's of luncheon meat naturally living in thie swim gimme a break.
As for salmon they do feed in freshwater although it hasn't been proven that they get anything out of the food they eat,i hear u shout lies,lies,over here in little old ireland,we fish the mayfly and numerous grilse and salmon are picked up on the dry , wet mayfly's and on dapping the natural,when u spoon them they are full of mayfly's in their stomach and salmon can be seen on a calm evening wolfing down spent.
Additives play a large part in angling and alway's will,that's the fact's...