Author(s): Hiroki Aie; Yoichi Kawaguchi; Takahiro Sato; Takumi Akasaka

Linked Author(s): Takahiro Sato

Keywords: Dams; Sediment replenishment; Bat; Aquatic insect adults; Environmental assessment

Abstract: In a river with multiple dams, the physical conditions downstream vary depending on whether a sediment replenishment is in place (sediment supplied or riverbed degradation). In such cases, it is predicted that both the abundance and composition of emerging aquatic insects differ among reaches along the same river. Furthermore, we hypothesized that terrestrial consumers, such as insectivorous bats also are sensitive to their prey availability. We aimed to investigate differences in the emergence of aquatic insects from river reaches with different physical conditions of riverbeds formed by dams. And we further aimed to compare the acoustic activity of bats along the same reaches. The survey was conducted from late March to early May 2021 in the upper reaches of the Naka River, in Japan. There are three reservoirs along the mainstream of the Naka River. We established four study sites in three sections separated by dams, each with a different riverbed environment, and conducted biological surveys at each site. The composition of adult aquatic insects differed among the sections, although there were no differences in abundance. In the replenishment section, the proportion of Trichoptera and Plecoptera was higher than those of other sections. We further found that the acoustic activities of Myotis spp. in the replenishment section were significantly higher than those of other sections. These results suggest that Myotis spp. responded to emerging aquatic insects dominated in the sediment-supplied reach. Myotis spp. foraging on the water surface may be a good indicator to evaluate ecological responses to sediment replenishment.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p1292-cd

Year: 2023