| In this study, we propose a method for habitat evaluation of water-column fish that focuses on the velocity profile, which is spatially heterogeneous in the roughness layer. Experimental testing is conducted using three different methods for evaluating the habitat volume of swimming fishes within the velocity profiles of four different bed conditions. In order to investigate flow characteristics of the boulder-bed, the first set of experiments are performed within a large flume. After confirmation of correct velocity conditions, the activity of living, swimming fish is observed in those conditions as the second set of experiments. Opsariichthys platypus (Zacco platypus), one of the dominant fish species among Japanese fresh water fish, is employed for the living fish experiment. Based on the results of the two experiments, the accuracy of these three methods is discussed. The first method uses a special and depth-averaged velocity, the second method uses a velocity profile averaged in the same height of each vertical transects and porosity profile of the bed, and the third method uses the velocity profiles from each of the vertical transects. In summary, the second method was found to provide a quantitative estimation for fish habitat with changes in river bed condition if the spatial averaged velocity profiles are known or predicted by another model such as DANS. |
