Fish location data based on PIT

The establishment of hydropower projects have affected the flow regime and structure of fish habitats. Various habitat restoration measures based on natural river morphology have been carried out, but the effects of habitat restoration and the hydrodynamic mechanisms of fish preferred topography remain unclear. Based on a large ecological test site, we created a variety of near-natural microtopographic habitats and achieved real-time monitoring of behavioral characteristics of the test fish habitats by deploying a Radio Frequency Identification (RFID) system incorporating Passive Integrated Transponder (PIT) tags. The experimental results indicate that microtopographies with different structures have a certain attraction to fish behavior. Among the four selected hydrodynamic indicators, flow velocity and vorticity have a greater effect on Onychostoma sima (O. sima). The optimal vorticity for fish habitats ranges between 1.75 and 10.85 s⁻¹, with suitable flow velocities exceeding 0.545 m/s. The hydrodynamic mechanism of habitat selection for the test fish is presented according to the Habitat Suitability Index (HSI) and Regression Tree (CART) methodology. The results have verified by the Receiver Operating Characteristic (ROC) method showed that the habitat selection model based on hydrodynamic indicators has a good prediction effect on the determination of suitable habitat for most test fish. In this study, we explored the relationship between fish activities and hydrodynamic indicators in complex terrain, and obtained the utilisation patterns of fish for different habitats under changing terrain and flow conditions. It provides theoretical support for flow scheduling and habitat terrain management under the influence of hydropower projects.

Methods
We adopt the passive integrated transponder (PIT) radio frequency identification system to monitor the habitat behavior of fish in the self-constructed area modelled after the natural river in the ecological test site.