2019 Volume 75 Issue 2 Pages I_1001-I_1006
The shape of a structure capable of mitigating the impact of hypoxia in water environments where hypoxia occurs in all layers from the bottom to the top was studied. The Amagasaki Canal is chronically hypoxic; occasionally all layers are hypoxic. The only fish confirmed to live in this canal throughout the year is the benthonic fish Tridentiger obscurus. This study showed that if a structure with gaps is installed in the surface layer, when only the bottom layer is hypoxic, the fish uses it as a substitute habitat. When all layers are hypoxic, the fish swims above the plate submerged near the water’s surface to obtain aminiscule amount of reaerated oxygen and raise its nose to the surface. Under this condition, Tridentiger obscurus’ preference for and tendency to occupy gaps is absent. The aforementioned observations show that an effective means to mitigate the impact of hypoxia on Tridentiger obscurus is installation of structures with gaps and a bottom surface that the fish can settle on near the water surface.
