Abstract
Surrounded by upright sheet-pile walls, the Amagasaki Canal is in a hypoxic state for over half of a year, making it an extremely severe environment for the survival of aquatic organisms. As a measure to restore the canal environment, we conceived of installing a structure with interstitial spaces near the water surface where the water is less affected by hypoxia, thereby, enhancing the canal functions as a habitat for aquatic organisms. In this study, we used Tridentiger obscurus, a demersal fish that is predominant in the Amagasaki Canal. We performed laboratory experiments under different dissolved oxygen levels, light conditions and installation position of the interstitial space and observed the behavior of Tridentiger obscurus. Our results showed that these fish changed their behavior depending on the light conditions. They also showed a strong preference for the interstitial space under all tested condition. When the bottom layer of the canal was deoxidized, they stayed around the interstitial space near the water surface. The interstitial space was also suggested to reduce the stress due to hypoxic conditions.
