Underwater sound: Its relevance to behavioral functions among fishes and marine mammals

A brief history of the development of underwater bioacoustics (from the early 1960s on) is provided, particularly as it relates to the theoretical problems confronting directional hearing in fishes and its experimental resolution as well as the resulting change that occurred in the interests of many workers, i.e., from understanding the acoustical and associated functional problems confronting the whole animal to understanding the neural and sensory mechanisms of hearing. Several topics are then discussed: (1) functional aspects of acoustical communication (interplay among sensory modalities and sound structure), (2) functional aspects of interception (some insights into old problems), and (3) orientation in space (independent of animal interactions) by fishes and marine mammals. The author concludes that although studies are demonstrating an expanding functional role of sound in the lives of fishes and marine mammals, speculation continues to play a large role. Such speculation has strong heuristic value, however, when based an careful observation and an awareness of the often complex nature of underwater acoustics.