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

Possible pitfalls in fish passage research and how to avoid them (#70)

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

The worldwide expansion of hydropower as well as the need for ecological improvements of riverine biological communities have prompted intensive research and monitoring of fish passage, yet many procedures and protocols have not been sufficiently validated. This presentation investigates some of the most common assumptions and pitfalls in fish passage research and provides concrete recommendations of how they can be avoided. This includes the following examples: (1) the bias introduced by various catching /monitoring techniques, (2) the transferability of findings from fish passage laboratory experiments to real situations, (3) the replacement of experiments with real fish by modeling and sensor fish experiments, (4) the optimization of fish ways for the sole purpose of increasing passage, as well as (5) the assumption that innovative hydropower techniques would always be more fish friendly than conventional ones. A systematic study on the above points comprising nine sites with innovative and conventional hydropower use revealed that (1) even advanced sonar- and camera-based monitoring tools can introduce substantial bias in terms of fish counts and sizes and that net-based catches can result in high injuries and mortalities under certain conditions. They also revealed (2) strong discrepancies in the efficiency of downstream passage fish guiding devices between laboratory and field, as well as (3) between modeling and sensor fish experiments and the damage observed in real fish populations. Moreover, it is suggested that (4) fishways can also have important functions as substitute habitats in addition to their function for fish passage, and that (5) some of the innovative hydropower techniques can result in mortalities higher than in conventional Kaplan or Francis-turbines. All of these findings suggest that the development of standards in fish passage research requires further optimization to increase comparability of data from across sites.