Author(s): Helmut Mader; Andreas Brandl
Linked Author(s):
Keywords: No Keywords
Abstract: Actual European and International guidelines are raising the demand for an attraction flow between 1% and 10% of competing flow at the fish pass entrance. In this ongoing research project key stimuli at bypass entrances were evaluated. In this content, it was examined if rheo taxis of fish will have a positive effect on the number of fish migrating into fish passes. Fish passage has been monitored over 2 years at the entrance of technical fish passes in large epipotamal and large hyporhithral rivers. The attraction flow at the fish passes entrances was controlled. The bandwidth of the variation of discharge in the fish passes in combination with the natural fluctuation of the discharge in the rivers leads to an attraction flow in the range of 0.1 to> 10%. A first screening of the relationships between the tested random variables took place by means of correlation analyzes. A further selection of the variables affecting the ascending of individuals occurred in two stages. In stage one; relevant predictor variables are identified by the LASSO (least absolute shrinkage and selection operator) regression analysis. In stage two, the result of the Lasso regression was tested using the step by step approach of the selection of variables of the STEP algorithm. The statistical analyzes of the reaction of fish following the stimulus of attracting current showed no significant change or increase of number of individuals entering the fish passes. Finding the entrance was independent from the availability and strength of a guiding current.
Year: 2018