Swimming speed measurement of Pacific saury (Cololabis saira) using Acoustic Doppler Current Profiler

Abstract

) migratedoffshore Funka Bay of Hokkaido using an acoustic Doppler current profiler (OceanSurveyor, RDI,153.6kHz) established in T/S Ushio-maru of Hokkaido University, in September 27, 2003. The ADCPsdoppler shift revealed as the raw data that the maximum swimming velocity was measured 163.0cm/s, andits horizontal swimming speed and direction were 72.424.1 cm/s, 160.122.3 while the surroundingcurrent speed and direction were 19.68.4cm/s, 328.1 45.3 . To calculate the actual swimming speed ofPacific saury in each bins, comparisons for each stratified bins must be made between the mean surroundingcurrent velocity vectors, measured for each stratified bin, and its mean swimming velocity vectors, assumedby reference (threshold70dB) and 5dB margin among four beams of ADCP. As a result, the actualaveraged swimming velocity was 88.6cm/s and the averaged 3-D swimming velocity was 91.3cm/s using the3-D velocity vector, respectively. Keywords: Acoustic Doppler Current Profiler, Pacific saury, swimming speed, 3-D velocity vector