Journal of the Japan Society of Erosion Control Engineering, Vol.58,No.3,2005
The physiological impact of turbid water caused by sediment flushing on
fish
and a prediction method
Atsuhiko KINOSHITA Masaharu FUJITA @Masatomo TAGAWA Takahisa MIZUYAMA Toyoaki
SAWADA
Abstract
To evaluate the impact of sediment flushing on fish, we need to predict the physiological
impact of turbid water. For some indices used to evaluate the impact, the concentrations
of suspended solids and dissolved oxygen are very important. In this study, we
clarified the mechanism of the physiological impact of turbid water on fish and
constructed a model that calculates the rates of mortality, or asphyxiation, based
on the concentrations of suspended solids and dissolved oxygen.
First, we examined the temporal variation in the concentrations of suspended solids
and dissolved oxygen at three sites subject to sediment flushing. Then, we conducted
two tank experiments. The first investigated the relationship between the concentration
of suspended solids and the mortality rate of char with sufficient dissolved oxygen,
and the second examined the physiological impact of an increase in the concentration
of suspended solids. Third, we modeled the results of the tank experiments. We
postulated that as the concentration of suspended solids increases, the volume
of oxygen absorbed decreases as the gills become covered with sediment. Finally,
we examined the physiological impact of sediment flushes at the three sites using
the model.
The tank experiments showed that an increase in the concentration of suspended
solids and a decrease in the concentration of dissolved oxygen both lead to asphyxia.
Given the temporal variation in the concentrations of suspended solids and dissolved
oxygen, the model has the potential to roughly estimate the rates of mortality
or asphyxiation of fish.
Key words: sediment flushing, fish, suspended solids concentration, dissolved
oxygen concentration
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