Worms are a bait fishers favorite bait, and a favorite of fly fishermen in the know. There's a simple reason worms work for bait: fish see them often and they like to eat them. Many different waters have populations of aquatic worms and terrestrial worms are washed into streams and rivers by runoff and rain storms. Worms are a high-protein trout food that big fish like. Try fishing a San Juan worm in your favorite stream, river, or lake and you may be surprised with a lunker on the end of the line.