Fishways as Downstream Routes in Small Hydropower Plants: Experiences with a Potamodromous Cyprinid

Francisco Javier Sanz-Ronda,Juan Francisco Fuentes-Pérez,Francisco Javier Bravo-Córdoba,Ana García-Vega

doi:10.3390/w13081041

Francisco Javier Sanz-Ronda, Juan Francisco Fuentes-Pérez + Show 2 more

Open Access

https://doi.org/10.3390/w13081041

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Abstract

Fish need to move upstream and downstream through rivers to complete their life cycles. Despite the fact that fishways are the most commonly applied solution to recover longitudinal connectivity, they are not considered viable for downstream migration. Therefore, alternative facilities are recommended to facilitate downstream migration. However, a few recent studies have disagreed with this general assumption, showing the potential for bidirectional movements. This study advances our understanding of the potential of fishways for downstream migration by studying their efficiency in a run-of-the-river hydropower plant in the Duero River (Spain). To achieve this, downstream movements of the Iberian barbel (n = 299) were monitored in a stepped fishway for two years with passive integrated transponder (PIT)-tag technology, considering the effect of fish origin and release zone. The results showed that 24.9% of barbels descended through the fishway, with the origin and release zone affecting the fishway location. In addition, downstream movements were observed throughout the whole year, except in winter. The study concludes that, under specific scenarios, fishways could act as safe alternative routes for downstream migration.

Highlights

Many fish species display migratory movements between different habitats as a strategy to optimize their fitness and complete their life cycles [1,2]
It is possible to find fish species that complete their life cycles in marine environments, strictly riverine species, and even species that share different stages between seas and rivers [2]. These movements may differ between individuals in a population, with the existence of some fish that only develop short movements and others that complete long-distance movements [3,4,5]
The hydraulic characterization of the river section allowed us to identify the area of the turbine intake as the most probable attractive route for downstream migration, as it provided a larger area of high flows than the intake of the fishway (Figure 4)

Summary

Introduction

Many fish species display migratory movements between different habitats as a strategy to optimize their fitness and complete their life cycles [1,2]. It is possible to find fish species that complete their life cycles in marine environments (oceanodromous), strictly riverine species (potamodromous), and even species that share different stages between seas and rivers (diadromous) [2]. Migratory behavior is a complex and variable phenomenon which shows differences between species, life stages, individuals, and regions [2] Rheophilic potamodromous cyprinids, such as barbels (genus Luciobarbus and Barbus), perform movements during most of the year, with the greatest migratory activity taking place during spring and early summer. During this period they ascend to the headwaters for reproduction [6,7], looking for shallow waters with high oxygen concentrations, gravel and pebble bottoms, and a moderate current velocity [8,9]. From late summer to autumn, barbels move to overwinter places [14,15], where they enter a dormancy period during winter (i.e., without activity) as a consequence of the low temperatures [6,16]

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