Ethohydraulic experiments on the fish protection potential of the hybrid system FishProtector at hydropower plants

Abstract The FishProtector, an Electric Flexible Fish Fence is investigated in ethohydraulic experiments. Fish protection potential is tested using an outdoor, experimental channel. To find optimum parameter settings, cable clearance, approach flow angle, and the size of the electric field vary within predefined limits. Due to the combination of both, the physical barrier (tensioned steel cables) and the behavioral barrier (pulsed electric field in the low voltage range), fish protection no longer depends solely on cable clearance. Generally, all investigated setups with combined physical and behavioral barriers show mean fish protection rates of higher than 97%. Cable clearances of 60 mm (largest cable clearances investigated within this study) show the same fish protection rates as cable clearances of 30 mm, each in combination with an electric field. The setup was a non-scaled section-model of a runoff river power plant. The behavioral experiments were performed with wild and PIT-tagged brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), grayling (Thymallus thymallus), and chub (Squalius cephalus). Measured body lengths were between 100 and 285 mm. The FishProtector with wide cable clearances and moderate electric fields in both size and voltage significantly improves the fish protection rate, showing significant potential for operating hydropower plants.