Used to do that on a lake in Wyoming when we were kids. We would wade out far enough to cast to the grass where the gills were spawning. We filled up 5 gallon buckets day after day with gills.We would use a small weighted fly with light spinning gear and a bobber, and if you put a little peice of nightcrawler on the end of the hook they will hold on to a little bit longer increasing your catch 10X.