After previous projects to assess fish behavior (Cuchet ISE 2012) and fish protection (Geiger ISE 2014) at horizontal intake screens, the final stage of the research program clarified the details of fish downstream migration with regard to screen passage and injury and mortality during turbine passage. Therefore the behavior of almost 2000 inserted individuals of brown trout, grayling, barbel, minnow and bullhead of 45 mm to 22 mm body length was investigated in a large scale test facility which included a 35 kW hydro power plant under nature like conditions but also enabled targeted hydraulic situations and modifications of the bypass. Additional tests with immobilized fish and different types of fish dummies were conducted to account for the influence of the swimming capacity and body shapes on the damage rates.

A recapture rate of the fish of 99 % and a subsequent observation period yielded detailed information about the migration behavior and instant as well as long term injury and mortality. Physical modelling of the damage processes combined with statistical modelling of the obtained results derived the underlying relations for injury and mortality rates of fish during turbine passage. The comparison of the results with different literature references for fish mortality during turbine passage identified those approaches suitable for small scale hydro power setups. Furthermore the inclusion of statistical modelling of the screen passage yielded prognosis for the ecological impact of hydro power setups in dependency of the facility configuration, its service conditions and the exposed fish population.