Abstract:
Reduction of fish mortality at hydropower facilities is an intense field of research for Power Companies. Nowadays, reduction of turbine capacity seems the most efficient methods, but require to be able to restrict the turbine management operations precisely to fish migration peaks to reduce loss of production to its minimum. Based on the IchtyosTM fish counting system that we use regularly to assess fish upstream migration in fish passes with a combination of laser-beams and video records, we recently adapted this technology to a silver eel specific pipe-like bypass installed at two hydropower facilities in Germany. The association of infrared-cells and video records allowed us to record automatic detection results and video samples on a local hard disk remotely connected. A specific algorithm is being developed over the study still on going with very encouraging results in terms of counting and measuring eels. The system is intended to send an automatic signal to an operator in case of eel passage detections who will then confirm it by the associated video sequence to finally start a turbine management procedure if necessary. One counting device could be used to manage several successive HPP in a river system based on real lecture of fish migration, while several devices might be required as local factors could influence eel migration patterns. This system presents the advantages to be a passive observation method, which is not invasive for fish, contrary to fish telemetry that needs to catch and surgically tag the fish. However, telemetry studies are still very important to assess fish behaviour and for instance improve the position of a fish counting system in the vicinity of HPP. Moreover, the global efficiency of an automatic counting and warning system can only be assessed by the use of telemetry studies
