Author(s): Melanie Mueller; Joachim Pander; Josef Knott; Juergen Geist
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Abstract: Knowledge on the extent and mechanisms of fish damage caused by hydropower facilities is important for their ecological assessment and improvement. In this context, objective monitoring of turbine -related fish injury is a necessity. Such monitoring depends on standardized procedures for fish recovery at turbine outlets, injury assessment, as well as consideration of handling effects on fish that must be distinguished from hydropower -related damage. Herein, we propose a novel fish injury assessment protocol suitable for a standardized and field-based evaluation. It is based on five general health criteria and a detailed severity assessment of 9 lethal and sublethal injury types across 18 body parts, resulting in a total of 86 damage combinations. The protocol was validated using 5,349 specimens from 32 central European fish species. Injuries related to handling and to contact with different parts of the hydropower structure could be clearly distinguished and assigned applying multivariate statistics. In a next step, catch-related injuries caused by four different fish recovery installation designs were assessed, considering exposure time, floating debris (different composition and amount), fish biomass and current speed inside the traps. Exposure time and the construction scheme of the fish recovery unit had the strongest effects on catch-related damage, being up to 150-fold increased after 12 h compared to 1 h in net units covering 100% of the discharge. Depending on the fish species, box designs versus classical fyke-net designs resulted in different damage patterns of captured fish. Besides exposure time and construction details, higher current speed and biomass within the traps resulted in greater fish damage. To minimize catch-related effects, keeping emptying periods < 12 h as well as considering and reporting current speed, fish and debris biomass are crucial to increase data comparability among studies. In conclusion, minimizing catch- and handling-related fish damage as well as standardized injury assessment is essential to help identify hydropower technologies and operational procedures which minimize harm to fish.
Year: 2018