FishMASS: what can you do with a little bandwidth when you are watching fish?

FishMASS (Fish Monitoring Acoustic Sensing System) is an NSF-funded project designed to adapt broadband acoustic Doppler current profiling (ADCP) technology to split-beam fisheries sonar. ADCPs use Doppler methods to observe ocean current profiles, and split-beam sonars locate targets within well-calibrated beams to determine target strength, and indirectly, fish size distributions. Combined ADCP/split-beam sonars would have the obvious advantage of enabling a split-beam sonar to measure a component of a fish´s velocity. It turns out that broadband signal processing, now standard in ADCPs, offers other less-obvious benefits too. Wide acoustic bandwidth enables more precise single-ping echo intensity measurements and better separation of closely-spaced targets and it provides information about the echo spectrum. This paper reviews these new capabilities and describes a prototype FishMASS system now being used for laboratory and field investigations