3Graduate School of Agriculture, Kyoto University
Rockfishes of the genus Sebastes along the coast of North America, for example S. flavidus, S. caurinus and S. maliger, have homing ability to their original habitats after experimental displacements. We found that the black rockfish S. inermis in Japan had also a homing ability resulting from the biotelemetry experiment. We used the V-test to determine whether the homing behavior was random or orientated. The black rockfish moved at random within some hours after release. Four hours after release, they moved to their home site intentionally. However, homing mechanisms of these rockfishes have not been clarified at all. Therefore we conducted the other biotelemetry experiment to clarify the homing mechanism of black rockfish S. inermis. We focused on the visual cue and the olfactory cue of the homing navigation. In our vision blocked experiment (n=14), the elapsed time for the blind fish to home was not significantly different from that for the control fish. In our olfactory ablation experiment (n=10), all intact fish homed to their original habitat. In contrast, all ablated rockfish with vaselin in its nares did not return to their original habitats. The rockfish might also home after the removal of vaselin from its nares. These results show that the olfaction is the major sensory mechanism of the black rockfish to detect the original habitat.