| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
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.
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