Initial Results from a Portable Dual-Beam Sounder for In Situ Measurements of Target Strength of Fish

A portable 105-kHz dual-beam sounder has been field tested for two years. Data have been obtained on the target strength of standard targets, adult sockeye salmon and juvenile and adult Pacific herring. White Halex ping-pong balls have been the most uniform standards with a TS of -39.1 dB. The TS/kg for adult sockeye salmon is -32 dB/kg and for juvenile and adult Pacific herring -26 dB/kg.