Author(s): Yoshiki Shiraishi; Kouki Onitsuka; Takayuki Nagaya; Makoto Higashino; Tohru Takami; Noriharu Otsuka; Juichiro Akiyama; Hiroaki Ozeki
Linked Author(s):
Keywords: Habitat; Suitable habitat; Territory of ayu; Field survey
Abstract: Ayu, Plecoglossus altivelis, inhabits in Japan, Korean peninsula and the east of the continent of China. Ayu makes their territory almost in the rapids and sometimes in the pools. However, this reason is not known. A field survey was conducted by authors. A territory of ayu was found near the large rock in the pools. Measurements of the flow depth and three components of velocity were conducted in this territory. It was found that the velocity distributions are described by the log-law and turbulence intensity distributions are described by Nezu & Rodi (1986) ’s empirical formula in the territory except for very near the rocks, so that the flow characteristics is not different from those in pools. Further, the depth and bulk mean velocity in the habitat of ayu were investigated. It was found that nevertheless the depth and bulk mean velocity is suitable for inhabiting of ayu, sometimes ayu can not inhabit, when the duration time and also the sunshine duration after the flood is not enough for growth of attached algae. This implies that sometimes unsteady model is necessary when suitability for ayu is investigated.
Year: 2005