Fundamental Study on the Recapturing Method for the Conditioned Fish School

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The fundamental study was conducted on the possibility of recapturing the conditioned fish of parrot bass Oplegnathus fasciatus and red sea bream Pagrus major by the acoustic and visual complex stimuli, in a tank (18*8*1.3m) for three years since 1986. The intermittent sound (500Hz sound of 5 seconds transmitting at 2 seconds interval) was employed as the acoustic stimulus. A visual screen was a cylinder type of 1 meter in diameter, consisted of eight steel bars and an center pole of 1 meter height having the colored stripe of black and white. The screen was suspended from the floating device (3*3m) and rotated by the motor at the speed of 4rpm. The process of the conditioned reflex of fish to the acoustic and visual stimuli were examined with the numbers of feeding trial. After the completion of the conditioned reflex of fish, several experiments were carried out for the detailed discussion on the extinction of the conditioned reflex in relation to the environmental change and the duration of the un-reinforcement period. With the reinforcement by the feeding trials, the conditioned reflex was require in 4-5 days. Parrot bass showed the superior ability in the retention of the conditioned reflex after several breaks of the re-training. According to the comparative observation of the fish behaviour in the tank, the floating device and the motor noise were considered to affect the nature of the acoustic and visual stimuli for the conditioned reflex. After the transportation of fish to the different tanks, red sea bream showed almost the similar behaviour, while parrot bass not showed it. Judging from these results, it will be more effective for recapturing the conditioned school that the complex stimuli are used.