Relevance of key stimuli, in particular light and acoustics, for the findability of fish passes

Brandl, Andreas; Käfer, Sabine; Fillitz, Benjamin; Pinter, Gabriel; Laaha, Gregor; Mader, Helmut

Relevance of key stimuli, in particular light and acoustics, for the findability of fish passes | Relevanz von Schlüsselreizen, im Besonderen Licht und Akustik, zur Auffindbarkeit von Fischaufstiegen

2020

The findability of entrances of fish passes for fish, following their instinct movements triggered by key stimuli serve as a basis for addressing a wide range of research issues. The present project is part of a multi-stage study which aims to determine key stimuli which are responsible for finding the entrance of fish passes. Mainly the attraction flow and the flow impulse have been mentioned in the literature and especially in guidelines for planning of fish passes so far. Out of a hydraulic point of view, the area of flow pattern downstream the entrance affected by the attraction flow or flow impulse is limited. Up to now, there is a lack of field trials that correlate the ascent behaviour of the population of migrating fish individuals with environmental stimuli. In the study described in this article, the data of the spring and autumn monitoring of the FAH in 2019 at the Edling/Drava hydropower plant were analysed. In addition to the stimuli of the various flow parameters, two additional artificial stimuli, addressing the phonotaxis and the phototaxis, were set. On the basis of the time accurate recording of each individual ascending, the connection between the key stimuli acoustics and light and the detection, respectively the ascent rates in the fish pass was examined by means of technical, fish ecological and mathematical methods. In addition to the FishCam system for 24/7 accurate detection of fish movements and the FishNet software, statistical methods for variable selection based on penalized regression models with different penalty terms such as LASSO, SCAD and MCP came into operation. As a result out of the field study, additional phonotactic and phototactic key stimuli had no positive effect on the findability of the fish pass entrance.

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