Acoustic methods of fish detection have proved essential in profitable fisheries. Recent improvements in electronics have led to better performance, reliability, and reduced equipment costs. The operation and interpretation of the information provided by modern acoustic equipment requires skill and practice. This manual contributes, in a practical way, to the speedy acquisition of these essential abilities. Although compiled primarily for fishermen, instructors, extension workers and trainees, it will also be found useful for boat owners, fishery managers, and administrators in helping to select and install the best acoustic equipment for a particular fishing purpose.