Abstract
Fish are particularly sensitive to connectivity loss as their ability to reach spawning grounds is seriously affected. The most common way to circumvent a barrier to longitudinal connectivity, and to mitigate its impacts, is to implement a fish passage device. However, these structures are often non-effective for species with different morphological and ecological characteristics so there is a need to determine optimum dimensioning values and hydraulic parameters. The aim of this work is to study the behaviour and performance of two species with different ecological characteristics (Iberian barbel Luciobarbus bocagei–bottom oriented, and Iberian chub Squalius pyrenaicus–water column) in a full-scale experimental pool-type fishway that offers two different flow regimes–plunging and streaming. Results showed that both species passed through the surface notch more readily during streaming flow than during plunging flow. The surface oriented species used the surface notch more readily in streaming flow, and both species were more successful in moving upstream in streaming flow than in plunging flow. Streaming flow enhances upstream movement of both species, and seems the most suitable for fishways in river systems where a wide range of fish morpho-ecological traits are found.
Highlights
The increasing demand of water for human consumption propels the construction of dams and weirs that become insurmountable barriers to the migration of fish, imperiling the completion of the life cycle of several fish species
Horizontal plane 2 of this flow regime was characterized by a velocity peak close to the inlet of the water plunge that shaped a short downstream jet-flow region, interrupted by the main upstream flow
At horizontal plane 1 of the streaming flow regime, a large jet-flow region going from the water inlet to the opposite cross-wall could be observed
Summary
The increasing demand of water for human consumption propels the construction of dams and weirs that become insurmountable barriers to the migration of fish, imperiling the completion of the life cycle of several fish species. More than half of the world’s largest rivers are currently negatively impacted by dams and weirs [1], which have caused serious declines of both resident and migratory fish populations [2] by affecting upstream adult migration, reproduction, feeding and colonization movements, while promoting genetic impoverishment and dispersion of exotic species [3]. To overcome this problem, barriers must become negotiable by fish. Several non-salmonid species have acquired greater legislative protection (e.g. under the EU Habitats Directive [7])
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