Author(s): David Faro; Christian Wolter

Linked Author(s):

Keywords: Habitat suitability; Functional connectivity; Larval drift; Population dynamics modelling

Abstract: In -stream habitat enhancement is widely used to improve ecological conditions, often targeting key fish life stages like spawning and juvenile development. Despite widely applied revitalization, there is nearly no quantitative target setting or benchmarking, nor standardised approaches to predict measure effects on recruitment and population dynamics. We applied a spatially-explicit population dynamics model that integrates habitat availability, quality and functional connectivity to assess the recruitment potential for four rheophilic and lithophilic fish species (grayling, nase, barbel, and chub) in a section of the Inn River (Germany). The impacts of two restoration measures (a bypass channel and an island side-channel system) were evaluated. Model results suggest that the improved habitat conditions increased fish population densities on average by 14.9 ind./ha. However, limited accessibility of suitable nurseries was identified as key recruitment bottleneck. We also examined an alternative spatial configuration of implemented measures, which increased nursery habitat availability from 33.2% to 95.3%. Enhanced functional connectivity substantially increased recruitment potential, although species responses varied due to differing sensitivities to spawning-to-nursery habitat ratios. This study demonstrates the applicability of the integrated modelling approach and underscores the need to consider habitat ratios and connectivity to effectively enhance fish recruitment.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.253

Year: 2026