Effectiveness of a multi-slot vertical slot fishway versus a standard vertical slot fishway for potamodromous cyprinids

Abstract

Developing and testing new fishway designs is important to improve these facilities. Discharge-efficient passage systems are required in Mediterranean regions and other areas with dry climates. The present study compares the passage performance of the Iberian barbel, Luciobarbus bocagei (Steindachner, 1864), a potamodromous cyprinid, negotiating two different types of vertical slot fishways (VSF): a standard VSF and a multi-slot VSF (MSF). Results show that differences exist between configurations in the number of fish movements through the first slot. The I. barbel performed a significantly higher number of movements in the MSF. However, no differences were found in the entrance time and entry efficiency. The performance was similar between configurations in terms of successes, suggesting that both fishways could be used to restore longitudinal connectivity. Nevertheless, the MSF is a more discharge-efficient configuration, since it requires 31% less water to operate for the same water depth in the pools. Consequently, the velocity and turbulence have lower magnitudes which generally favour the negotiation by smaller individuals. Since it is a more discharge-efficient and cost-efficient configuration, future studies should focus on the passage performance of smaller species to determine if MSF is a useful solution for the whole fish community.