In‐stream habitat improvement drives fish recovery in restored meanders: insights from the Demer River

Abstract Introduction Freshwater fauna are increasingly threatened by habitat degradation and climate change. Rising flood frequency and magnitude underscore the need for river restoration to enhance ecosystem resilience. While restoration is widely promoted, outcomes for freshwater fish remain inconsistent. Success depends heavily on restoration design, water quality, and bio‐indication tools. Yet, many studies lack an approach that considers fish demographics, assemblages, and habitat characteristics simultaneously. Objectives This study assessed the effectiveness of remeandering designs on fish communities at both the river and reach scale. We evaluated ecological outcomes using multiple metrics, including the ecological quality ratio (EQR), species composition, demographics, life‐history traits, and environmental drivers. Methods Fish and environmental data were collected in restored and control reaches over 4 years post‐restoration and compared with historical reference data. We evaluated spatial and temporal trends and assessed how specific restoration designs influenced fish metrics. Results Five years post‐restoration, no significant river‐scale improvements in EQR were observed. However, several restored reaches showed clear local improvements. A positive trend over time highlights gradual ecological recovery and reflects the disruptive effect of a flash flood 1 year post‐restoration. The reach with a more complex restoration design exhibited higher juvenile abundance, broader reproductive guild diversity, and more complete age‐class structures. Conclusions While river‐scale improvements were limited, reach‐scale results demonstrated that restoration design is crucial in driving fish recovery. Habitat diversity, conceived through in‐stream adaptations, emerged as a key factor for success.