Cognitive aspects of food searching behavior in free-ranging wild Common Carp

Although laboratory experiments have shown that many fishes, Goldfish (Carassius auratus) in particular, employ relatively sophisticated orientation strategies to learn the location of food in laboratory arenas, this ability has not been rigorously tested in the natural environment. In this study we documented the ability of Common Carp (Cyprinus carpio), a close relative of Goldfish, to learn the location of newly introduced food in a lake. Two experiments were conducted, the first of which determined that carp feed largely at night. The second used this information and tracked the day- and night-time locations of 34 radio-tagged carp before and then while a food reward was introduced at a specific location in the lake for 10 days. Before the introduction of the reward, carp maintained small (similar to 100 m x 70 m), isolated home ranges which expanded slightly at night. This movement pattern changed after the reward was added when on the fourth night six radiotagged carp visited and exploited the reward and then returned to their home areas after sunrise. This pattern persisted for the rest of the experiment with increasing numbers of carp visiting the reward each night (21 of 34 carp visited on the tenth night) and returning to their home ranges each day. The speed and precision with which wild carp learned to exploit this reward is consistent with the social learning and spatial memory skills that they and their relatives have shown in laboratory arenas. This is particularly impressive given the turbid conditions in the lake and the lack of obvious visual landmarks.