Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Seasonal and diurnal variation of downstream fish movement at four small-scale hydropower plants (#153)

Josef Knott 1 , Melanie Müller 1 , Joachim Pander 1 , Juergen Geist 1
  1. Aquatic Systems Biology, TU Munich, Freising, Germany

Hydropower plant structures and other obstacles hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on natural patterns of fish downstream movement is necessary. So far, migration behavior of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of non-migratory species or medium-distance migrators. In this study, fish movement patterns in four different impounded rivers were assessed and compared with the fish community composition in the headwater of the hydropower plants. There were strong differences between the fish community composition inhabiting the headwater and the fish detected in downstream passage. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught per hour during the night (2.9 fish/h) than during the day (1.3 fish/h). In all study rivers, Pseudorasbora parva, Thymallus thymallus, Sander lucioperca and Cottus gobio mostly moved downstream during the night. During the day, the most frequent downstream moving fish were Rutilus rutilus, Alburnoides bipunctatus and Alburnus alburnus. There was a significant positive relationship between the number of downstream moving specimens and turbidity, water temperature and the discharge of the four investigated study rivers. Following the strong differences in seasonal and diurnal fish movement patterns, fish damage can be strongly reduced with adaptive turbine and corridor management.