Author(s): Maria Joao Costa; Francisco Godinho; Filipe Romao; Juan Francisco Fuentes-Perez; Jeffrey Tuhtan; Antonio N. Pinheiro; Isabel Boavida

Linked Author(s): Isabel Boavida

Keywords: Hydropeaking; Iberian cyprinids; Artificial lateral line; Movement behaviour; Habitat

Abstract: Hydropower plants that operate in hydropeaking to respond to electricity demand, introduce rapid and artificial flow fluctuations in the downstream river system. These can alter the river hydromorphology ultimately affecting downstream habitat availability and biological processes. Fish habitat selection during rapidly changing flow conditions remains poorly understood, especially at the reach system scale. The objective of this study was to relate fish habitat use with the hydrodynamic conditions after a peak event has occurred. To understand the role of flow changes on fish habitat selection at this spatial scale, we characterised the hydrodynamic conditions of specific habitats along a 140 m northern Iberian river reach located downstream of a small hydropower plant. After tagging 134 cyprinids (Pseudochondrostoma duriense n = 108; and Squalius carolitertii n = 26) with passive integrated transponders, fish were tracked using a portable telemetry antenna for five consecutive days, immediately after the peak events. The peak discharge fluctuated between 1-2 m3/s. The total detection rate was 67%, of which 77% were P. duriense and 23% were S. carolitertii. To characterise the hydrodynamic conditions, we selected representative areas of fish presences and absences, upstream and downstream of the HPP. Grounded in the functioning of the mechanosensory lateral line system, the hydrodynamic conditions were measured with an artificial analogue, the lateral line probe. Three derived pressure variables were selected: mean front pressure, mean pressure fluctuations, and mean pressure asymmetry. These are related to the streamwise flow velocity, turbulence intensity, and asymmetric fluid-body interactions. Preliminary results indicate that fish presences were associated with lower fluctuations and asymmetry. The highest fluctuations and asymmetry were observed in areas where fish were not detected, whereas both presences and absences occurred in the whole range of mean front pressure. With this study, we expect to provide novel insights regarding the role of the hydrodynamic conditions at the reach system scale for habitat selection by small-sized cyprinids affected by hydropeaking. In addition, we expect to demonstrate the utility of using this biomimetic technology to understand the importance of the hydrodynamic environment and propose habitat enhancement solutions.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221269

Year: 2022