The FishProtector – An Integral Fish Protection System

The need for an effective fish protection system was triggered by the European Union with the introduction of the EU Council Directive 2000/60/EEC (Water Framework Directive) in the year 2000. While the upstream migration of fish has been object of research for a long time and various measures have proved successful, the state of knowledge in terms of fish protection and downstream migration has to be increased. Especially for medium to large sized hydropower plants, effective mitigation measures are largely missing.

Therefore, the Unit of Hydraulic Engineering (University of Innsbruck) developed a new, integral Fish Protection System, based on horizontally arranged steel cables. These are installed in front of the turbine inlet in a way that fish are protected and guided to a bypass. At the same time, the cables can be used as electrodes to create an electric field in the adjacent waterbody. Hence, the FishProtector combines the advantages of a physical and a behavioral barrier.

The fish protection efficiency as well as the guiding efficiency of the system were quantified and assessed in ethohydraulic experiments for various potamodromous species. Further, the behavior of fish in close proximity to the FishProtector was observed and classified, using underwater cameras. Additionally, promising preliminary experiments with European eels were performed.

The results of the ethohydraulic experiments show, that the electric field around the steel cables (combination of physical barrier and behavioral barrier) causes very high fish protection rates and enables a larger spacing between individual cables while maintaining the fish protection rates. Further, fish are guided along the FishProtector, showing a typical behavior pattern in close proximity to the barrier. Verified by a huge number of empirical data, the knowledge stock in terms of downstream fish migration and fish behavior in close proximity to a barrier (slight differences by species are obvious) could be increased. The main advantages of the FishProtector are lower construction and operational costs, compared to conventional fish protection systems.