Visiting Researchers

CRI Visiting Professor 2005/6

Dr. Shin Hyeon-Ok, Professor
Dept. of Marine Production Management
Pukyong National University
599-1 Daeyeon-dong, Nam-gu, Busan 608-737, Korea
Tel: 051-620-6125; Fax: 051-622-3306
Email

Dr. Shin’s Research - Analysis on the movement of bag-net in set-net by Telemetry Techniques

Abstract

The authors reconstructed a mooring type underwater positioning system to measure the latitudinal movement of a bag-net in a set-net by the telemetry techniques with five transponders. The field experiments were carried out in Jaran Bay, Kosung, Korea on October 6, 2000 (neap tide) and November 28, 2000. The longitudinal movement range, the latitudinal one and the vertical one of the bag-net at the neap tide were 3.2 m, 3.4 m and 2.1 m, respectively. At the spring tide, these variations were 7.8 m, 7.8 m and 5.0 m, respectively. The vertical oscillation range at the bottom of the bag-net near the point of the  slope net, at the middle part and at the far point from the slope net were 3.2 m, 3.7 m and 8.4 m, respectively. The depth of the bottom net was decreased and its vertical oscillation appeared frequently when the current speed was more than 10 cm/s and the current direction was significantly different from the longitudinal axis of the bag-net. The variation of hydrophone coordinates measured by the transponder fixed on the sea bed presents that hydrophones equipped to the frame line of the set-net could be moved within several meters due to the tidal current. This fact indicates that the compensation of hydrophone coordinates is necessary to reduce the measuring errors. The underwater position fixing errors of x-axis, y-axis and z-axis of the system measured in the cage of aquaculture were 0.6 m, 0.8 m and 1.2 m, respectively. Also, the errors of the transponders that were close to the baselines or placed in the baselines were smaller than those in other position.