Frequency response of the swimbladders of fish

Abstract

The gas-filled swimbladder of a fish resonates in the ambient noise field, scattering significant amounts of acoustic energy. This characteristic scattered field is thought to assist a fish's own hearing and also may allow for the detection and identification of other scatterers by the receiver [P. H. Rogers et al., J. Acoust. Soc. Am. Suppl. 1 85, S35 (1989)]. The frequency response of the swimbladder can be measured in vivo by a noninvasive vibration amplitude measurement system [M. Cox and P. H. Rogers, J. Vib. Acoust. Str. Rel. Des. 109, 55–59 (1987)]. The response for a variety of fish of the species Carassius auratus (common goldfish) and Astronotus ocellatus (oscar) was measured and correlated with respect to fish size. One aspect of the results further examined was the appearance of twin peaks in the response of some goldfish. X rays of the subjects indicated that differences in size of the anterior and posterior chambers of the swimbladder may be responsible. [Work supported by ONR.]

Measuring the acoustic scattering response of small groups of live fish in a laboratory tank

“…It has been previously reported in the literature that goldfish bear a two-chambered swim bladder [8,9], and experimental results show that the interaction between the two chambers of the swim bladder leads to a two-peak resonance phenomenon, which can be modeled as an oscillating system with two degrees of freedom. According to Finneran and Hastings [10], the goldfish swim bladder chambers are both roughly prolate spheroidal in shape, with an average major/minor axis ratio of about 1.44 to 1.66.…”

Biomechanics of the Acoustico-Lateralis System in Fish

“…To examine this, the data was compared to a generalized curve for scattering cross-section, This method of data presentation differs from that used before (Cox, 1987;Lewis et aL, 1991) which gave results in terms of relative motion. It can be shown (Appendix A) that the scattering cross-section is proportional to relative motion squared.…”

“…Results from previous experiments in this lab (Cox, 1987;Lewis et al, 1991) were given in terms of relative motion. Appendix A shows the mathematical relationship between scattering cross-section and relative motion.…”