Author(s): Renan Leite; Maria Joao Costa; Daniel Mameri; Fernando Afonso; Antonio Pinheiro; Jose Maria Santos; Isabel Boavida
Linked Author(s): José Maria Santos, António Pinheiro
Keywords: No Keywords
Abstract: The impacts of artificial pulsed flows associated with hydropower production on the downstream biological and physical processes have been extensively addressed, particularly those affecting fish fauna, causing fish drift and forcing changes in habitat selection. Our knowledge of these impacts in improving habitat enhancement strategies is still limited, especially for cyprinids. The goal of this study was to evaluate the attraction efficiency of two flow-refuges differing in their approaching angles, for the Iberian barbel (Luciobarbus bocagei, Steindachner 1864) at an indoor experimental flume. We tested two flow-refuge approaching angles i. e., 450 and 700, creating distinct hydraulic conditions at the flow-refuge entrance. Two flow events, i. e., a base (BF) - and a pulsed-flow (PF), were tested for each flow-refuge type. To analyse flow-refuge efficiency, we quantified fish individual and group use patterns (absolute frequency and permanence time) at two distinct refuge locations (downstream and inside) and physiological responses (glucose and lactate). The flow field was characterized using an ADV probe. The results showed that the individual frequency of use during the PF events was higher, especially for the 45º angle. Significant differences in the frequency of individual use, inside and downstream of the area of the flow-refuge, among flow events were found. The use in group of the flow-refuge did not show a significant effect in neither inside nor downstream locations of the flow-refuge. There was no statistical evidence that the position of the flow refuge affected the group behavior of barbels under PF. Although the PerMANOVA did not show significant results for the overall metrics, the permanence time as an individual uses inside the 45º flow-refuge tends to be higher than the 70º flow-refuge, during PF events. The flow events and the approaching angles tested did not trigger physiological responses in the tested trials. Overall, the 45º flow-refuge tended to be used more often than the 70º. The flow field differed between the two insertion angles. The 45º flow-refuge induced channel narrowing and subsequently creating greater flow uniformity. This enhanced flow homogeneity likely contributed to increase the flow-refuge use by fish. These findings emphasize the critical importance of carefully selecting the insertion angle when designing and installing flow-refuges for cyprinids, particularly in river ecosystems impacted by pulsed flows.
Year: 2024