Asymmetry of the behavioral response in roach Rutilus rutilus (L.) (Teleostei: Cyprinidae) to a new object

The young roach Rutilus rutilus (L.) (Cyprinidae) displays lateralized behavior when facing a barrier through which a simulated bigger fish was visible. The asymmetry consists in a significant tendency to detour a barrier rightwards in the presence of a dummy fish. However, asymmetry is insignificant without the model. A comparison with the available literature shows that the roach has the same direction of this lateral bias as some other shoaling cyprinid fishes, which also preferentially turn to the right in the presence of a dummy fish. This seems to be a characteristic of cyprinids, as opposed to species of some other families displaying a leftward bias or a lack of asymmetry. The results of the study testify to the hypothesis that behavioral lateralization is associated with the taxonomic status of fishes. Currently, it is unclear whether the asymmetry found in roach in a detour test is due to the preferential use of the lateral fields of the right and left eyes as in some other fishes, or if it is a result of motor lateralization, which becomes evident in the presence of an unfamiliar and potentially dangerous object.