Fish Movement Analysis in Diagonal Brush Fish Pass: Innovative Approaches

The fish behavior and flow structure of the diagonal brush fish pass were monitored and investigated simultaneously at the Incirli Small Hydropower Plant (SHP) which is in the Eastern Black Sea in Turkey. It has been shown that the reduced velocity and turbulence regions behind the brush blocks constitute important resting sites for fish and the macro-scale vortices with vertical axis formed in the stream environment can help fish in their upstream migrations. The main advantage of brush fish pass appears to be the fact that it provides passage for small-bodied fish (Lf < 0.15 m) in a high gradient bed slope of 10%. We propose a computer vision-based approach for fish movement analysis. The proposed approach detects fish and estimates the fish tail beat frequency automatically, while the fish trajectory is obtained manually. The framework is tested using visible-range videos captured by cameras installed in the lab environment and the field. Fish Strouhal number calculations for different fish trajectories are presented. In the field experiments, fish Strouhal number is in the range of 0.04–2.10 and higher fish Strouhal numbers indicate higher fish swimming costs. The field measurements reveal that a wide spectrum of different flow characteristics is provided in the diagonal brush fish pass. The cleverness of the fish is used to seek convenient corridors and to avoid zones not suitable for their migration preferences.