Measurement of Diurnal Body Tilt Angle Distributions of Threeline Grunt Parapristipoma trilineatum Using  Micro-Acceleration Data Loggers

Hideaki Tanoue; Teruhisa Komatsu; Alabsi Natheer; Isamu Mitani; Shinichi Watanabe; Yuuki Watanabe; Akira Hamano; Nobuyuki Miyazaki

Measurement of Diurnal Body Tilt Angle Distributions of Threeline Grunt Parapristipoma trilineatum Using Micro-Acceleration Data Loggers

2013

The body tilt angle of a fish has a large effect on the acoustic target strength. For an accurate estimation of fish abundance using acoustic methods, it is necessary to measure body tilt angles in free-ranging fish. We measured diurnal body tilt angle distributions of threeline grunt (Parapristipoma trilineatum) while swimming in schools in a fish cage. Micro-acceleration data loggers were used to record (for 3 days) swaying and surging accelerations (at 16 Hz intervals) of 10 individuals among 20 forming a school in a fish cage. Time series analysis of 1-h mean body tilt angles revealed significant differences in body tilt angles between day (−7.9 ± 3.28°) and night (0.8 ± 5.89°), which must be taken into account when conducting acoustic surveys. These results will be useful for calculating the average dorsal aspect target strength (TS) of threeline grunt for accurate estimations of fish abundance.

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