Analysis on the movement of bag-net in set-net by acoustictelemetry techniques

ABSTRACT:   A mooring-type underwater positioning system (UPS) to measurethe bag-net movements in a set-net by acoustic telemetry techniqueswith five transponders was reconstructed. The field experimentswere conducted in Jaran Bay, Kosung, Korea on 6 October 2000 (neaptide) and 28 November 2000 (spring tide). The average UPS fixingerrors of x -axis, y -axis and z -axis were less than0.6 m, 0.8 m and 1.2 m, respectively.The longitudinal movement range, the latitudinal range and the verticalrange of the bag-net at the neap tide were 3.2 m, 3.4 mand 2.1 m, respectively. At the spring tide, these rangeswere 7.8 m, 7.8 m and 5.0 m, respectively.It was confirmed that the UPS system could be used for measuringa part of the bag-net movement.     

Behavior of Israeli carp Cyprinus carpio traced by long baseline telemetry techniques during dynamite explosion work

ABSTRACT:   The swimming behavior trajectory of an Israeli carp (body length 28 cm) during dynamite explosion work was obtained by the long baseline acoustic telemetry system with an ultrasonic pinger in an aquaculture cage located at Chungju Lake on 2 May 1997. The underwater noise levels measured at a distance of 400 m from the source of noise increased by 40 dB (re 1 µPa) compared to the levels before the explosion. The swimming area of the fish was reduced immediately after the explosion but more than 1 h after the explosion the fish had returned to a similar swimming area and behavior as right before the explosion. The fish usually swam less than 1.5 m from the water surface except during or right after the explosion. When there was an external stimulus, such as, an explosion the fish swam downwards. The average swimming speeds of the fish before, during and after the explosion were approximately 0.33 m/s, 0.52 m/s and 0.29 m/s, respectively, and the average swimming speed of the fish during the explosion was 1.6 times faster than usual.