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Gewählte Master / Diploma Thesis:

Roman Burtscher (2022): Salmonid Movement: Effects of a drawdown flushing on the movement behavior of fish in the River Möll.
Master / Diploma Thesis - Institut für Hydrobiologie und Gewässermanagement (IHG), BOKU-Universität für Bodenkultur, pp 108. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Sediment-management in alpine hydropower reservoirs is challenging. Operators must find solutions to get rid of the alluvial deposit to preserve reservoir storage, at the same time the negative effects of a drawdown flushing on the living environment in downstream river stretches have to be kept to a minimum. To provide a scientific explanation of the acute impact of a drawdown flushing on the downstream freshwater ecosystem, individual fish movement was investigated in two river sections of the River Möll, Carinthia, Austria. In this mark-recapture study (MR) all together 6 978 salmonids (age 1+ onwards) were marked with passive integrated transponder (PIT) tags and observed for more than a year. Movement variables like ‘turnover-rate’, ‘individual displacement’ and ‘proportion of sedentary individuals’ were assessed for brown trout, grayling and rainbow trout. Salmonid movement was restricted during summer in both river sections. Within the study sections the flood including a drawdown flushing in October 2018 led to enhanced mean movement (365 m/Ind.) than the flood event itself (198 m/Ind.). Findings regarding the two size classes (< 201 mm and > 200 mm) were limited. Recolonization behavior showed species-specific differences. After displacement, in August 2019 more than 80 % of recaptured graylings and brown trout returned to formerly occupied habitats in the control section, while recolonization movement was restricted for rainbow trout (57%). Most investigated fish were missing after the drawdown flushing in the residual flow section. Since it remained unclear, where the tagged individuals stayed, the study design should be optimized: additional application of telemetry techniques, enhanced electrofishing effort immediately after the flushing event, extension of the impacted study section or continuous marking throughout the investigation period is recommended for future investigations with regard to the effect of a drawdown flushing on salmonid movement.

Beurteilende*r: Schmutz Stefan
1.Mitwirkender: Pinter Kurt

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