Multi-year movements of potamodromous cyprinid species within a highly anthropized river assessed using RFID-equipped fishways

Abstract

Movements of potamodromous fish are poorly understood, especially in large rivers, because studies often focus on fishway evaluation and diadromous species. Here, we assessed the movements of 808 fish of five potamodromous species (Barbel, Barbus barbus; Common bream, Abramis brama; Nase, Chondrostoma nasus; Asp, Leuciscus aspius and chub Squalius cephalus) over 14 years in a highly anthropized river system, the Rhine River, where hydropower plants were progressively equipped with fishways including RFID antennas. The objectives of the study were 1) to characterize long-term and large-scale individual movement patterns of five potamodromous fish species 2) to assess inter- and intra-specific variations based on quantitative movement metrics and 3) to create a typology of individuals based on their movements. Results showed that, despite high intra-specific variability, the inter-specific differences were strong enough to highlight long-term and large-scale species-specific behaviors. Breams exhibited movements that occurred essentially during spawning migration period and at the reach scale. In contrast, barbels were more active, with more movements outside their spawning migration period, showed more large-scale and downstream movements, and used navigation locks more often than other species. For this species, the maximum distance between the two furthest recorded positions at the basin scale was exceptionally high (max = 155 km). We conclude that potamodromous species undoubtedly perform large-scale movements, which are characterized by both species-specific and common features. Therefore, efforts need to be made to better consider their ecological needs and swimming capabilities when planning and designing effective fishways for the diverse range of species that move within river systems.