Book & DVD. During the considerable periods of time trout spend feeding exclusively on underwater food forms, nymph fishing can be the most productive, if not the only way to catch fish. But understanding what occurs below the water's surface can be a challenge for even the most experienced angler. In "Nymph-Fishing Rivers and Streams", aquatic entomologist and long-time fly fisherman Rick Hafele shares the information necessary to successfully decipher...