MARUOKA and Haruo IWASE : The influence of bedrock outcrop on stream fish habitat, and the assessment of restoration in a bedrock stream channel. Ecol. Civil Eng. 12 1 , 57-66, 2009. Abstract: In March 2006, six spur dikes consisting of several sets of the wired boulders, were experimentally placed to restore gravelbed in a 50-m bedrock outcrop reach of the Makomanai River, central Hokkaido, northern Japan. The study purposes were to examine the influence of bedrock outcrop on summer habitats

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... wrinklehead sculpin Cottus nozawae and masu salmon Oncorhynchus masou , and spawning habitat of masu salmon returning from ocean. The effects of spur dikes on habitat improvement were also examined. We set three sections representing gravelbed reference , bedrock control and experiment treatment , and investigated physical habitat variables, fish density and the number of masu salmon redd from July to October 2007. In the bedrock section, areal percentage of gravelbed was distinctly lower than that in the gravelbed section. Sculpin abundance and the number of redd were also lower in the bedrock section than in the gravelbed section. In the experiment section, abundance of small-sized sculpin 90 mm and the number of redd were similar to those in the gravelbed section, owing to an increase of gravel-pebble 2-64 mm area in the experiment section facilitated by the spur dikes. Abundance of large-sized sculpin 90 mm in the experiment section was lower than that in the gravelbed section because area of cobble-boulder 64 mm suitable for large-sized