Later, as the earth once again warmed and as the ice sheets melted, shriveled, and pulled back, many species such as the brook trout were cut off, left to adapt or vanish. The brook trout survived by moving up the rivers into the colder waters of mountain streams where it flourished on crawfish and minnows and an abundant supply of insects. And the brook trout thrived until the loggers came, until the streams were stocked with rainbow and brown trout. Pressed by new competition from man and other trout, the brook trout fled, moved higher and higher. Trout find it difficult to tolerate each other's presence, especially in smaller streams and rivers.
Trout are bullies.
Rainbows will press and drive off specs, just as sooner or later the big browns will press and drive off the rainbows. Not too many years ago a rumor spread through the high country like the windblown fog that fills every valley, cove, and hollow. The rumor was that the Park Service, in a sudden fit of creative management, was actually considering poisoning the streams of the Great Smoky Mountains National Park in an effort to rid the park's trout waters of renegade rainbow and brown trout, thus ridding the specs of their enemies and their competition. It caused considerable discussion and comment and not a little excitement until someone chanced to ask just what kind of magic poison, what grand elixir was so marvelous, so selective and discriminating in its killing that you could taint a river with it and yet it would do away with rainbows and brown trout and not harm anything else. It sounded as though the Park Service had come up with the piscatorial equivalent of the neutron bomb a concoction that would kill certain species of fish without upsetting the stream's ecosystem at all.