Scattered ambient noise as an auditory stimulus for fish

Abstract

In an earlier paper [P. H. Rogers, J. Acoust. Soc. Am. Suppl. 1 79, S22 (1986)], it was hypothesized that one role of the fish's auditory system may be to detect and localize nearby fish by “imaging” ambient noise scattered by their swim bladders. This is analogous to the role of the visual system of most animals, where the relevant signal is ambient light scattered by objects rather than light emitted by luminous objects. A classical conditioning experiment has been performed which indicates that the fish auditory system is capable of functioning in this manner. The ambient noise is provided by a J‐9 transducer driven by Gaussian noise. Scattering of this noise by the resonant swim bladder is simulated by applying a filtered version of the noise signal to a small spherical projector. The “target strength” is bandwidth of the filter. The fish is conditioned to respond to the presence of the signal from the spherical projector. The fish's ability to detect this signal (as a function of range, bearing, etc.) is taken to be a measure of its ability to detect scattered ambient noise.