Post-release performance and dietary overlap of hatchery-reared Brown trout: Implications for restocking management...

Restocking programmes aim to enhance depleted wild fish populations by releasing hatchery-reared individuals. This study evaluated the growth performance and dietary overlap between hatchery-reared and wild Turkish brown trout (Salmo trutta Linnaeus, 1758) in the Çağlayan River, northeastern Türkiye. Over 18 months, growth metrics including length-weight relationships, condition factors and specific growth rates were assessed. Results demonstrated significant growth in hatchery-reared trout following initial acclimatization, with similar growth trajectories to wild fish. Dietary analyses through stomach content examination revealed a substantial dietary overlap between hatchery-reared and wild individuals, with both groups primarily consuming Plecoptera, Diptera and Ephemeroptera. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) confirmed no significant differences in diet composition between groups, suggesting successful dietary acclimation of hatchery trout to natural prey. These findings highlight both the potential benefits and ecological risks associated with restocking, emphasizing the importance of careful management to mitigate competition and ensure genetic integrity of local trout populations.