The present study was made in order to analyse the factors which release the behavior of the carp, Cyprinus carpio LINNE, that is snapping at the tip of a glass funnel. The fish being conditioned to feed a fish meal diet introduced through the glass funnel were used.
The results can be summarized as follows;
1) The snapping behavior is released by setting of the funnel alone, as well as by the introduction of the water sampled from the aquarium (control water) or by that of the water containing some chemical components from the food (extract solution).
2) The snapping response to the fixed funnel alone or the inflow of the control water becomes most active during the period of 50 min. to 1 h. 40 min. prior to the regular feeding time, but lowers very much after the real feeding. And then they increase again after the period of 4 to 7 hours of this low activity.
3) The frequency of snapping activities is observed to be the lowest in the case of the response to the funnel alone. Those in the response to the inflow of the control water are higher by 0.26 freq/min/capita than the previous ones. And finally the frequency of the response to the inflow of the extract solution is the highest, remaining at a higher level than that of the response to the control water by 1.17 freq/min/ capita.
4) The comparison of the frequencies of the snapping activities under various experimental conditions with each other make it possible to analyse the stimulus signal releasing the food-searching behavior in the fish.