2014 Volume 20 Pages 67-72
Riverbed is consisted of various habitat types, e.g., riffles, pools, side pools, back waters, etc. These habitats are changing in time and space by deposition and erosion processes caused by floods. These processes should be appropriately considered in the ecological evaluation. This article discusses riverbed characteristics of spawning redds for Ayu, in relation to changing patterns of habitats in the Tenryu River. Firstly, we conducted field surveys over November to December 2013 and found two spawning redds at small riffles in channels flowing from the spring welling up in a side pool. Physical characteristics of the spawning redds were identified based on the DO concentration and riverbed softness measured at the various habitats in the field. Spatial and temporal changing patterns of the habitats suitable for spawning redds were also investigated using the images of interval-recording- cameras installed at the study site for analyzing habitat scale changes and aerial photos for reach scale changes.
