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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME A: Engineering and Management of Fresh-water Systems : Seasonal changes of feeding behavior of ayu, plecoglossus altivelis altivelis
Seasonal changes of feeding behavior of ayu, plecoglossus altivelis altivelis
Author : Takayuki Nagaya, Kouki Onitsuka, Yoshiki Shiraishi, Makoto Higashino, Tohru Takami, Shinji Matoba, Juichiro Akiyama, Hiroaki Ozeki, Yoshinobu Akaki
It is necessary for inhabitation of aquatic lives such as fish, crab and so on, to preserve the structure consisting of both pool and rapid. Because some fish prefer pools and the other fish prefer rapids. In particular, the ayu, Plecoglossus altivelis altivelis, prefers rapids. The ayu is one of the most expensive fish in fishery in Japan. However, the reason why the ayu prefers rapids has not been investigated. In this study, the field surveys, i.e., velocity measurements, flow depth and bed level measurements, recording the behavior of the swimming ayu and also gathering attached algae on the rocks, were conducted both in the pools and rapids under the condition that the ayu cannot feed attached algae in some area (non-ayu area) and also that the ayu can feed in the other area (normal area). Such experiments were conducted several times during spring to autumn, because the ayu inhabit in the river during spring to autumn. It was found that the growth rate of attached algae in the rapid is larger than that in the pool. The growth rate of attached algae in non-ayu area is larger than that in the normal area, due to the ayu feeds attached algae on the rocks in the normal area. A logistic model was used for the evaluation of the growth rate of attached algae. As a result, the difference in the growth rate of attached algae between in the pool and rapid and also that between in non-ayu and normal area can be investigated quantitatively. Further, the seasonal change of such characteristics will be investigated.
File Size : 355,890 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME A: Engineering and Management of Fresh-water Systems
Date Published : 01/07/2007
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