Abstract
Most fishway studies are conducted during the reproductive period, yet uncertainty remains on whether results may be biased if the same studies were performed outside of the migration season. The present study assessed fish passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei), in an experimental full-scale vertical slot fishway during spring (reproductive season) and early-autumn (non-reproductive season). Results revealed that no significant differences were detected on passage performance metrics, except for entry efficiency. However, differences between seasons were noted in the plasma lactate concentration (higher in early-autumn), used as a proxy for muscular fatigue after the fishway navigation. This suggests that, for potamodromous cyprinids, the evaluation of passage performance in fishways does not need to be restricted to the reproductive season and can be extended to early-autumn, when movements associated with shifts in home range may occur. The increased effort during the non-reproductive period suggests that adapting the operational regime of fishways, at biologically meaningful seasons in a year, should be assessed by considering the physiological state of the target species.
Highlights
In-stream physical structures, such as dams and weirs, cause the disruption of longitudinal river network connectivity [1,2]
The present study focused on testing fish passage performance of the Iberian barbel, Luciobarbus bocagei (Steindachner, 1864), a potamodromous cyprinid fish, in a vertical slot fishway (VSF) during two distinct seasons: spring, the reproductive season for this species [27], and early-autumn, a non-reproductive season
Significant differences were found in the entry efficiency (F = 10.42, df = 9, p = 0.017), which was higher in early-autumn than in spring (Figure 3b)
Summary
In-stream physical structures, such as dams and weirs, cause the disruption of longitudinal river network connectivity [1,2]. Among the numerous impacts produced by these structures (e.g., water quality, sediment transport, biogeochemical cycles), they cause restrictions to fish movements by blocking the migratory pathways for fish populations [3,4]. The main mitigation solution to reestablish longitudinal connectivity for fish, when obstacle removal is not feasible [5]. The VSF remains operational across a wider range of upstream and downstream water levels, making this design a reliable option for managers [7]. The majority of fishway studies on potamodromous cyprinids are conducted during the reproductive migratory season [8,9], when fish are a priori physiologically motivated to swim upstream
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