NEUROETHOLOGICAL STUDY OF SALMON HOMING

姬鲑（湖栖红鲑鱼的一种，Oncorhynchus nerka；在北美被称为kokanee）洄游于中真次湖（日本枥木县日光市），成熟后返回家乡河流。在本研究中，为了进一步了解鲑鱼的嗅觉机制，我们研究了(1)嗅球对不同河水的脑电图反应（EEG）和(2)使用新开发的y形迷宫选择回家水的行为能力。结果表明：(1)电生理分析表明，大马哈鱼能够区分两条相邻河流（家河和非家河）河口的水；(2)实验行为分析表明，大马哈鱼对家水的偏好大于对非家水的偏好；(3)这种对家水的偏好以及上游行为在嗅觉器官损伤后严重受损。(d)因此，本研究为鲑鱼归巢的实验行为分析开辟了新的途径。

Hime salmon (lacustrine form of sockeye salmon, Oncorhynchus nerka ; known as kokanee in North America) migrate through Lake Chuzenji (Nikko, Tochigi Prefecture, Japan), and return to their home river when matured. In this study we examined, as a step towards understanding the olfactory mechanism for salmon homing, (1) electroencephalographic (EEG) response from the olfactory bulb to various river waters and (2) behavioral ability to choose the home water by using a newly developed Y-maze. As the results we found that (a) from electrophysiological analyses the hime salmon can discriminate between waters at the mouths of two neighboring rivers (home river and non-home river), (b) from experimental behavioral analyses the fish prefer the home water to the non-home water, and (c) this preference of the home water as well as the upstream-going behavior are severely damaged after lesioning the olfactory sense organ. (d) Thus, the present study opens a new way for experimental behavioral analyses of the salmon homing.