奈良県吉野川での底生動物の現存量 : II.1965年4月〜5月

概要

論文の詳細を見る
In April and May of 1965,the benthic communities were investigated by the quadrat (50×50 cm) sampling method at four stations along the River Yosino-gawa, with the following results : 1. At the station of Ikadaba in the upper reach of the river, Micrasema sp. a species of torrential caddisworms, which was very abundant in this station in Febrary, had remarkably decreased in number. Consequently, the total number of benthic animals had become reduced to a fifth of that in February. Their standing crops, however, showed nearly similar values between February and April. 2. At the other two stations, Sako and Gojo, situated in the middle course of the river, the standing crops of benthos had become reduced to half or a third of those in February. With the ratios of the standing crops among the three river-bed types, "Hirase"-rapid, "Hayase"-rapid and "Huchi"-pool, the definite trend that had been observed in February could not be recognized. Moreover, many river-bed types were marked with remarkable advances of several ephemerid species into dominant or subdominant positions. These three noticeable changes were observed for two or three months since February, and are considered to have been brought about by the marked decreases of net-spinning caddisworms, Stenopsychidae and Hydropsychinae, which showed some striking dominances at Sako and Gojo respectively in February.
日本生態学会の論文
1966-08-01