Selection of Iberian barbel Barbus bocagei (Steindachner, 1864) for orifices and notches upon different hydraulic configurations in an experimental pool-type fishway

Trends in fish passage studies are increasingly moving towards a holistic approach in considering the movements of a wide range of fish species and other aquatic fauna. In this context, it is important to consider not only salmonids and other game species, but also coarse species such as cyprinids. Moreover, knowledge of their behaviour when confronted with fishways is limited, particularly their upstream movements with regard to different hydraulic configurations. To address this deficit, research was conducted in an indoor full-scale pool-type fishway to assess the cyprinid Iberian barbel Barbus bocagei (Steindachner, 1864) response to the simultaneous presence of submerged orifices and surface notches with adjustable dimensions in association with two different flow regimes over the notches, i.e. plunging and streaming. Overall, orifices (76%) were the clear choice to negotiate the fishway. When the flow was in the plunging mode, a significantly higher proportion of fish selected the orifices to move upstream, but the proportions were equal during the streaming mode. The time taken to enter the fishway differed significantly according to the chosen discharge device and was lower for submerged orifices (52 s to 35 min.). The present study identified key factors in Iberian barbel upstream movements, which provide direct applications to future fishway designs for this species.