MEASUREMENT OF AUDITORY-THRESHOLDS OF THE TILAPIA TILAPIA-NILOTICUS

Auditory thresholds of the tilapia Tilapia niloticus in a quiet water tank were investigated using a classical conditioning procedure in a s table temperature container converted into an acoustic chamber. The cl assical conditioning procedure followed Ishioka's method. Tilapia coul d hear a sound band width ranging from 100 Hz to 1500 Hz with maximum sensitivity 300 Hz where the threshold was below 103.5 dB (0 dB re 1 m uPa). The background noise in the range of measurement frequency were in a low level of 37-47 dB (0 dB re 1 muPa/square-rootHz), and signal/ noise ratio in this investigation was above 50 dB. Nevertheless the au diograms for tilapia from 100 Hz to 1000 Hz were significantly higher than in the red sea bream. It is evident that the auditory capacity of tilapia is poor, as compared to that of the red sea bream tested by t he same method.