Author(s): Masayuki Fujihara; Kanaru Watanabe; Eiji Ichion; Shunsuke Chono; Tomoki Izumi; Hidekazu Yoshioka
Linked Author(s): Masayuki Fujihara, Tomoki Izumi
Keywords: Fish behavior; PIT (Passive Integrated Transponder) tag; Numerical simulation; Shichika irrigation canal; Diadromous fish
Abstract: Agricultural canals are generally equipped with tilting weirs, gates and hydraulic drops to control hydrodynamic conditions, which potentially hinder fish migration. The Shichika irrigation canal constructed in the alluvial fan of the Tedori river, Ishikawa Prefecture, Japan, has a series of tilting weirs and drops and discharges directly into the sea. Because of its connection to the sea, 11 species of diadromous fish have been found to use the canal. The purpose of this study is to estimate influences of the tilting weir conditions on fish migration along the canal. A computational model was developed to simulate the upstream migration of Ayu (Plecoglossus altivelis), a representative species of migratory fishes, based on the biotelemetry observation using PIT (Passive Integrated Transponder) tags in the Yamajima irrigation canal: a branch of the Shichika irrigation canal. The computational domain of the model consists of sub-models of channel and drop sections. In the channel section sub-model, Ayu is assumed to swim along the channel based on the characteristics of a swimming duration curve. In the drop section sub-model, Ayu is assumed to decide whether to swim or jump upstream based on the comparison of the velocity of falling water and Ayu’s burst speed. The computed results were validated by the observations of the time taken to pass two PIT tag antennas. And using identified parameters of Ayu’s swimming ability, simulated upstream migrations of Ayu through the canal of 3.5 km under various conditions of tilting weirs demonstrated that the conditions of tilting weirs had a significant effect on the upstream migration of Ayu.
Year: 2024