Abstract
Most freshwater fish need to move freely through rivers to complete their life cycles. Thus, river barriers that hinder or block their longitudinal movement (e.g., dams, culverts, gauging stations), directly affect their reproductive, feeding, and habitat routes. A holistic solution to these barriers would need to allow directed, undistracted, and bidirectional fish migration between different habitats; that is to say, it would need to allow two-way migration. The most extended solution that would allow upstream fish migration is a fishway. However, for downstream migration fish have alternate routes such as spillways, turbines, or bypasses. Studies and discussions about two-way migration and bidirectional movement through a fishway have been focused on large dams and reservoirs; thus, there is a lack of available data on other environments, less popular species, or smaller dams and weirs. In this sense, it is possible to hypothesize that a fishway, especially in a smaller facility, could enhance two-way migration by allowing bidirectional movement. Therefore, as a first step to analyzing the possibility, we studied longitudinal connectivity (two-way migration and bidirectional movements) through a small run-of-river hydropower plant (HPP) with a step-pool type fishway, a common and representative configuration of several small HPPs around the world. A potamodromous cyprinid—the Iberian barbel (Luciobarbus bocagei)—was selected as the target species. In this study, radio and PIT tracking data were collected for four different years and combined to characterize movement in the full system: fishway, turbines/spillways, and the river reach downstream (up to 3 km) and upstream (up to 4 km) from the HPP. The results demonstrated the existence of several types of movement with inter-annual and intra-annual variability. Several fish even returned over the years. This suggests that, in this type of HPP facility, a fishway can provide bidirectional connectivity and two-way migration, thus ensuring that a great proportion of fish complete their life cycles.
Author Contributions
Conceptualization, F.J.B.-C., L.F.-C., S.M. and F.J.S.-R.; methodology, F.J.B.-C., F.J.S.-R., A.G.-V. and J.F.F.-P.; validation, A.G.-V. and J.F.F.-P.; formal analysis, F.J.B.-C.; data curation, F.J.B.-C.; writing—original draft preparation, F.J.B.-C.; writing—review and editing, All authors; visualization, F.J.B.-C. and J.F.F.-P.; supervision, L.F.-C., S.M. and F.J.S.-R.; project administration, F.J.S.-R.; funding acquisition, F.J.S.-R. All authors have read and agreed to the published version of the manuscript.
Funding
This research was partially funded by the European Union’s H2020 research and innovation program under grant agreement No. 727830, FIThydro.
Institutional Review Board Statement
The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of University of Valladolid as well as the approval of the competent authorities, i.e. Regional Government on Natural Resources (Junta de Castilla y León) and Water Management Authority (Confederación Hidrográfica del Duero). (protocol code 7904309 and date of approval 3 august 2018).
Informed Consent Statement
Not applicable.
Data Availability Statement
Data are available upon reasonable request to the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
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