淡青丸による魚群探知機を用いた資源量推定に関する基礎実験

Abstract

In order to furnish quantitative information for population analysis, the develop-ment of a direct method to count the echo patterns of large sized fish individuals such as tuna, using a pattern analysis technique, was undertaken by the Division of Population Dynamics of Marine Organisms, Ocean Research Institute, University of Tokyo. The development of this direct method was started from 1967. For this project, basic experiments were planned by the staff of the Division and the authors conducted the said basic experiments on two cruises (KT-68-5, KT-68-24) of R. V. Tansei Maru (257.69 ton), University of Tokyo, on Sagami Bay in April and November 1968. The results are summarized as follows: 1) The maximum depth in which a single fish (Ts=-26dB) can possibly be detected by the use of the fish detector is about 150m. 2) The beam axis is inclined forward and the angle from the beam axis to the vertical axis is 3.54-4° 3) The range of the fork length of fishes (yellowfin tuna, rainbow runner and little tuna), hung by rope to a drifting buoy, was 50-130cm, and the range of target strength for those targets was -28.5 ?? -14.5dB. 4) The effect of ship speed on attenuation of received signal was measured with the effect of wind direction at three levels of ship speed. 5) Echo signals were recorded on magnetic tapes at several ship speeds when the ship passed near a buoy. The considerable variability of echo patterns was recognized even for the same buoy at the same ship speed.