Abstract
Fish protection at hydropower plants is important for the sustainability of hosting ecosystems and the acceptance of hydropower. On their way downstream, fish are exposed to hydropower plants and various related negative effects, ranging from a delay in downstream movement to being injured or killed by a turbine. Understanding the behavior of fish in close proximity to protection devices is essential in order to establish efficient fish protection facilities. In this study, physical (horizontal steel cables) and behavioral barriers (electric field) for fish protection were developed (Flexible FishProtector) and their effectiveness was investigated. The behavior of brown trout (Salmo trutta fario), rainbow trout (Oncorhynchus mykiss), grayling (Thymallus thymallus) and chub (Squalius cephalus) at the Flexible FishProtector was analyzed using video evaluation. The experimental setup was a non-scaled section model of a runoff river power plant. The used electric field induced a flight reaction at a corresponding distance to the Flexible FishProtector that significantly increased the protection rate. Furthermore, an increase in guiding efficiency was achieved with the use of a physical as well as a physical and behavioral barrier, supporting safe downstream migration with the narrower cable clearance (30 mm versus 60 mm).
Highlights
Fish migrate in rivers both up- and downstream to fulfill specific needs corresponding to their life stage, the time of the year, and environmental stressors [1,2,3]
Fish protection measures for downstream migration at hydropower plants have to be effective for various species and sizes
When a fish moved downstream, the physical barrier was perceived first and the fish took a positive rheotactic swimming position. This was the first fish reaction observed at a distance of approximately 0.5 to 1.0 m to the Flexible FishProtector
Summary
Fish migrate in rivers both up- and downstream to fulfill specific needs corresponding to their life stage, the time of the year, and environmental stressors [1,2,3]. Downstream migrating fish are still confronted with river fragmentation caused by hydropower plants. Trash racks in many cases cannot sufficiently prevent fish from entering the turbine passage [2]. Both turbine passages and the trash racks themselves can cause injuries and occasionally fatalities [2,14]. Fish protection measures for downstream migration at hydropower plants have to be effective for various species and sizes. Besides efficiently protecting fish from injuries, guidance is required to a safe downstream migration corridor without any appreciable delay [15,16,17,18,19]
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