Abstract
Fish spawning habitat preference was examined in an irrigation ditch of the Houki River in the Naka River system. Habitat types in the ditch were classified into five categories based on the physical characteristics of the environment. Eggs and larvae of Lefua echigonia and Cobitis sp. BIWAE type C, and eggs of Silurus asotus were collected in the ditch. Eggs of Lefua echigonia and Cobitis sp. BIWAE type C were observed in narrow, slow flowing, shallow areas out of the main current near the edge of the ditch in plant litter or vegetation. However, larvae of L. echigonia were found in wider and more vegetated areas in the main current than eggs. Eggs of S. asotus were found in wide, deep, slow moving areas in which litter and vegetation had been deposited. The findings of this study illustrated that the importance of microhabitat in spawning site selection, as well as the need to consider these factors when designing conservation measures for these species.
