Nippon Suisan Gakkaishi 69 (4), 575-583 (2003)

A method for target strength measurement of small-size animals by split-beam method in small tank

KAZUO AMAKASU, MASAHIKO FURUSAWA AND CHUMING FAN

Department of Marine Science and Technology, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan

We developed a precise method for target strength (TS) measurement of small-size animals such as krill in a water tank. The measurement system consists of a 70kHz split-beam system and a video camera system to observe the orientation of animals. The transducer was set pointing downward on the top of the small tank with a window on one of the side walls for observing orientation. TS measurement and orientation observation are performed simultaneously. This system can avoid external disturbances such as wind and waves and be set up easily for measurements including measurement on board a ship. TS measurement for a physical model (copper cylinder) was conducted and the measured TS was in good agreement with the theoretical result, showing the accuracy of our method. Next, TS measurements of live shrimps were conducted to get detailed TS patterns. We compared the measured results with the theoretical TS patterns and confirmed a reasonable agreement.


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