small, aggressive, fish will pretty much hit anything at any speed at any depth. Larger, quality fish want, the right size, colour, depth, and speed (which is very very slow)....especially for chronies. Sometimes when beginning to move to a new spot will trigger a strike as the fly is moved into the feeding zone of the fish...or the sudden movement triggers the strike. Better off anchoring and casting when using chronies...trolling you're better off using attractor or leech patterns. Trolling micro-leeches can be productive when trolling slowly. Years ago..I used Doc Spratleys as my searching pattern....then changed to leeches and micro-leeches.