Fish guidance structures: hydraulic performance and fish guidance efficiencies

Abstract The hydraulic performance and fish guidance efficiency (FGE) for behaviourally-based mechanical fish guidance structures, i.e. louvers and modified angled bar racks (MBRs), were evaluated experimentally and the results are presented herein. Detailed velocity profiling was conducted to assess the hydraulic performance of the 1:1 Froude-scaled racks in an etho-hydraulic laboratory flume. Guidance efficiencies of the studied rack configurations were evaluated through live-fish tests in the same flume. Tests were conducted with five European fish species, namely, barbel (Barbus barbus), spirlin (Alburnoides bipunctatus), European grayling (Thymallus thymallus), European eel (Anguilla anguilla) and brown trout (Salmo trutta). The results demonstrate that MBRs are advantageous over louvers because of reduced head losses, improved hydraulics and higher FGEs. Furthermore, use of a bottom overlay on the MBRs substantially increased the FGE. The results are discussed and compared with literature data. Recommendations for an optimized and economic MBR design are given. The present findings underpin the follow-up studies for further optimization of MBR design.