Author(s): Utashi Ciraane; Damien Sonny; Gaia Falgas; Archambeau Pierre; Dewals Benjamin; Michel Pirotton; Sebastien Erpicum

Linked Author(s): Michel Pirotton, Sébastien Erpicum

Keywords: Fish migration; Flow velocity; Meuse River; Numerical modelling; Fish tracking

Abstract: Important peaks in river discharge promote the seaward migrations of European silver eels (Anguilla Anguilla). However, such metrics are not easily transferable across rivers or on different river section s due to morphological differences in river cross-sections. Nonetheless, the flow velocity is a robust and replicable metric across rivers and a main component of the discharge. This study examined the relationship between the migration speed of fourteen silver eels and the mean flow velocity computed using a one-dimensional hydrodynamic model. The results revealed a strong correlation between both variables (Pearson r = 0.92| Spearman ρ = 0.91, p < 0.01). They also suggested that above a mean flow velocity of 0.4 BL/s ~ 0.4 m/s, the downstream migration was quasi-linearly correlated to the mean flow velocity, while it was slower than mean flow velocity below this threshold. These findings suggest that migrating eels favor high flow velocities, typically occurring during important annual peaks in river discharges. Thus, the flow velocity may serve as a more robust, reliable, and transferable metric for designing and implementing sustainable strategies and solutions for rapid and safe seaward migrations of silver eels in anthropized rivers.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.169

Year: 2026