PNNL

Abstract

The effect of the swimbladder on the source level and directionality of an acoustic fish tag signal was investigated through laboratory experiments and an analytical method. In laboratory experiments, the source level and directionality were measured in both a tag-only group and a tag-in-fish group. In the analytical method, both forward and backward scattering were calculated by assuming the acoustic tag was a point source and the swimbladder was a gas-filled spheroid. The mean source level of five tested tags decreased by ~4 dB after implantation in fish bodies, which is important for designing fish migration studies using acoustic telemetry.