Author(s): Paulo Branco; Ana Margarida Mascarenhas; Goncalo Duarte; Filipe Romao; Susana Dias Amaral; Maria Teresa Ferreira; Antonio Pinheiro; Jose Maria Santos

Linked Author(s): Paulo Branco, Susana Dias Amaral, António Pinheiro, José Maria Santos

Keywords: Fishways; Vertical slot fishways; River barriers; Meta-analysis; Freshwater fish

Abstract: Special Session: Ecohydraulics 2021: Novel methods to investigate flow-biota interactions numerically, in the lab and in the field Abstract Rivers are affected by a vast number of artificial barriers that block fish movements within river networks, preventing several freshwater dependent fish species from completing their life cycle. Fish need to be able to volitionally displace along river networks as their feeding, refuge and spawning habitats are spatially and temporally separated. This impossibility of free movement may result in within-population genetic homogenization, density reduction and potential extirpation, affecting metapopulation, and -community unbalance and disappearance. Altogether, this will lately contribute to species extinction and loss of community functional resilience, and, ultimately, disturbing ecosystems processes. Fishways are by far the most common approach to facilitate fish navigation along rivers, of which the most usual design is the pool-type fishway. Among these, the vertical slot fishways (VSF) are considered the best technical solution, because they remain operational even with fluctuating water discharges and allow fish to negotiate each cross-wall at their desired depth, catering to species with different ecological requirements. In this work, we have conducted a meta-analysis of published data on VSF for cyprinids native to Mediterranean river systems. We used Bayesian Generalized Mixed Models because they enable constructing models while accounting for random effects of non-controlled factors that may influence the model outcome, a valuable advantage when aiming to perform joint analyses of datasets with inherent data dependencies. The results demonstrate that it is possible to integrate outputs for different experiments, conducted in different years and seasons, and for different fish species. Results also show how fish size, regardless of species, is a strong predictor of fishway negotiation success. Overall, multiple slot fishways with one orifice proved to be the best solution, regardeless of fish species, and for all fish sizes. To improve the design of holistic fishways, future experimental studies should be focused on smaller fish and small fish species. Design guidelines for holistic fishways will benefit from this integrative approach, allowing for more effective connectivity solutions.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022980

Year: 2022