A conditioned response overrides social attraction in common carp: A possibility for low stress sorting strongly schooling fish?

摘要

In this study we investigated whether a conditioned response to a light cue can override the strong schooling tendency of common carp, with a view to identifying a possible system for low stress control of movement for captive fish. Carp were trained in groups of three to approach and bite a trigger to obtain food, the trigger being located next to a coloured light. In an initial pre-training period, fish were trained to approach and feed from a single trigger, identified by either a red, a green or a blue light; six groups were pre-trained with each colour. During 10 pre-training trials, II of the 18 groups learned to feed efficiently in this set up. These groups were then given further training with triggers at three potential feeding locations, again identified by red, green and blue lights, food being delivered from the trigger signalled by the colour on which the fish had been pre-trained. The position of the rewarded trigger was changed randomly between trials, which numbered 15 in all. All 11 groups learned to approach the rewarded trigger preferentially, though some sampling of unrewarded triggers continued. The learned response was strongest for fish trained to approach the red light. New groups were then constructed comprising one fish trained to each of the three colours. When released simultaneously in a position equidistant from a red, a green and a blue light, all unrewarded, the three fish swam independently towards the colour on which they had been trained. Besides confirming the ability of common carp to use a demand-feeding system and to associate a coloured light with the presence of food, these results show that individual fish can be induced to move away from a small group towards a coloured light as a result of differential training. The potential for using this capacity to control movement of common carp held in captivity, for whatever reason, is discussed. (C) 2014 Elsevier B.V. All rights reserved.