OHGUSHI, Ryoh-ichi and Yoko SAITO (Kyoto Univ., Kyoto) Ecological notes on the stream drifts in River Ukawa. Jap. J. Ecol. 13,28-35 (1963). Studies on the stream drifts in River Ukawa, Yosa Peninsula of Kyoto Prefecture were carried out in the summer of 1957 and 1960. The surpended materials flowing down in the river water were distinguished as follows ; sand and silt, organic debris, aquatic insects, exuviae of aquatic insects, fishes in young stage, and fragments of plants and terrestrial insects. Generally, the sand and debris occurred most frequently. Aquatic insects appeared in the stream drifts chiefly consisted of the nymphs or larvae of mayflies and midges. The contents of the collected materials were different according to the mesh of the collecting nets. Silt, debris and small insect larvae were caught by fine net (GG 72). On the contrary, the rough net (GG 40) caught the sand, leaves of tree and large insects. The volumes of collecting materials by the rough net were larger than that by fine net. The flowings of aquatic insects increase in night, but the daily rhythmic variations were not seen in the other materials. The volume of sand and debris contained in the water were varied with the parts of the river. The water in the upstream of the pool contained sand more of than that in the downstream. From the results of the above-mentioned investigations, ecological meanings of stream drifts are discussed.
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