A feeding device for fishes designed for experimental use

A demand feeder was designed and constructed for use in the conditioning experiments of fishes, with special attention paid to four points; that (1) it should provide only one pellet when the release mechanism is activated by the fish, (2) its trigger can be activated even by very light touch of the fish, (3) it should be protected from the actions of fishes other than those desired, and (4) it should be possible to manually activate the feeder whenvver needed. By using this device in conjunction with an electromechanical event recorder, a continuous record on the feeding activity of a bluegill sunfish for 10 days was obtained. The observations revealed that the levle of the feeding activity in the fish obtaining food from this device was much lower than that when the fish was fed by the experimenter.