Review: experiences with shallow water acoustics

Thirty years of experience in shallow water acoustic applications is reviewed in a variety of situations and environments. Particular attention is given to side-looking transducers, applied simultaneously with down-looking ones, in order to estimate fish distributed near the water surface. The success of side-looking operations is primarily limited by transducer and boundary characteristics, requires smooth water conditions but may generate double image echoes as a result of dual acoustic paths. Amongst the various modes of transducer deployment, the side-looking technique has the best spatial coverage but near-boundary detection is best with fixed location, particularly with recently developed remote, automated fixed location systems. Other problems are reviewed.