I have been fishing a stream the last couple of weeks. There has been a wonderful caddis hatch every evening at 730. The fish had been consistently small so I decided to try a section where I usually find larger fish. I arrived around 7 and fished until almost dark and not a bug in the air. When I left I crossed a bridge downstream and there were bugs everywhere. Any idea why? The sections of stream are separated by a 25 acre lake.