1965 年 15 巻 1 号 p. 18-24
When some reservoirs are constructed in the same river, the autochthonous environmental conditions of each lake and allochthonous limnological conditions caused by the inflow give remarkable effects on the aquatic communities of each reservoir. In this study, the Asahigawa Daiichi and Daini reservoirs among the four reservoirs constructed in Asahi River, were compared with the other two reservoirs from the limnological point of view. The results obtained from this study are as follows : 1. The environmental conditions of the Asahigawa Daiichi reservoir are similar to those of the Yuhara reservoir which is situated 30 kilometers above the Asahigawa Daiichi reservoir, and the plankton fauna of the former is about the same as that of the latter. As for the phytoplanktons, the pollution torelant species were found only in the former. From this result it can be said that the Asahigawa Daiichi reservoir is more eutrophic than the Yuhara reservoir. 2. In the Asahigawa Daiichi reservoir, some aquatic animals and plants were found in the shore zone. This phoenomenon is not generally found in other reservoirs constructed at about the same time. This phoenomenon seems to be caused by the following two circumstances. (1) Much organic matters or polluted water flow into this lake, making the lake eutrophic comparatively in a short time. (2) The shore of this zone is not too steep, therefore it has a comparatively wide shore zone, forming good habitats of the aquatic animals and plants. Furthermore the change of water level is so slight that the shore zone is not exposed in the cases of the low water levels. 3. The Asahigawa Daini reservoir receives the outflow of the Asahigawa Daiichi reservoir. The Asahigawa Daini reservoir is small in its volume, so the current velocity is fairly rapid compared with the other reservoir. The plankton flora and fauna of this lake is similar to that of the Asahigawa Daiichi reservoir.