There was a study once in Canada where the scientists picked a very, very remote river that had lots of trout and was never fished by sports fishermen.
They marked off a certain length of the river, and proceeded to ‘fish’ in the normal manner, catching their fish and measuring, weighing, noting when and where caught, etc. They caught and released over a hundred fish that one day.
The next day, they repeated the same sequence and failed to catch a single fish............................
Well, yeah. All the fish had sore mouths!