SEASONAL VARIATION OF BIOMASS AND RESPONSE TO FLOOD OF AQUATIC ORGANISMS IN TAKATSU RIVER

Abstract

 Environmental protection is regarded important along with flood control and water utilization in river management. Understanding the riverine ecosystem is necessary for such river management. In this study, we conducted monitoring on aquatic organisms in Takatsu River and tried to clarify the seasonal variations in biomass associated with the life history events for the dominant organisms (fishes, benthic invertebrates and attached algae). Furthermore, we examined the relationship between the intensity of disturbance (flow velocity and dimensionless tractive force) at the peak of the floods and the changes in biomass before and after floods. As a result, it was possible to capture the seasonal variations of biomass associated with the life history events such as the emergence and spawning of each organism. Moreover, a clear negative relationship between biomass and intensity of disturbance was found in four of nine taxonomical groups. The values of the intensity that make the biomass halved or disappeared were different among the groups.