Author(s): Keiko Muraoka, Yuichi Kayaba
Linked Author(s): Keiko Muraoka
Keywords: Fish passage, bottom-swimming fish, sculpin, ultra-high-speed camera, swimming physiology
Abstract: Most fish passages without natural fishways have been developed for strong-swimming species, such as salmonids. Although these passages have been designed to also accommodate weak swimmers, such as larval migrators, they create insufficient flow for the free migration of various species, especially bottom-swimming fishes such as sculpin. We propose including a cloister in fishway designs to facilitate the free movement of these weak swimmers. The scale of the cloister will depend on the body height of the targeted weak swimmer, but using an inclined ceiling would accommodate multiple fish sizes. In this study, small eaves have been installed along the lengthwise corner of the flow pipe to restrict sculpin from lifting their heads, and sculpin behavior in the flow was observed. Our results show that it is possible to optimize sculpin upstream movement by restricting head-raising movement using a design component such as small eaves. Although a maximum interior angle is effective for efficient sculpin migration, a 7. 5�25� interior angle and increased roughness on the eaves� surface is suitable for migration of both sculpin and goldfish. For sculpin to remain in the flow without drifting downstream, a 10� interior eave angle, flow velocity of 0. 5 m/s, and slippery acryl resin eave surface is the most effective combination. With slight roughness on the bottom, flow velocity of 0. 5 m/s, and no eaves along the corner, all the sculpins drifted down without migrating to the upper side. This result is also consistent with natural river bed conditions
Year: 2017