Environmental enrichment enhances feeding success during the early parr stage of Atlantic salmon (Salmo salar)

The release of hatchery-reared fish is a widely implemented management intervention aimed at supplementing or restoring declining wild populations. In Scandinavian rivers affected by hydropower development, stocking of hatchery‑reared Atlantic salmon (Salmo salar, Linnaeus, 1758) is commonly used to compensate for lost fishing opportunities when natural production losses in rivers are affected by hydropower development. Nevertheless, post-release mortality remains substantial, largely because fish reared under conventional hatchery conditions frequently exhibit insufficient behavioral competence for survival in natural environments, including underdeveloped predator-avoidance responses and suboptimal foraging proficiency. Previous studies suggest that environmental enrichment can promote behavioural development in Atlantic salmon (Salmo salar) parr, particularly when multiple types of enrichment—such as substrate complexity, water flow variation, and visual or structural features—are provided during raring. Here we show that structural enrichment alone after only 11–12 weeks exposure significantly improved feeding success on novel live prey in parr compared to individuals reared in unenriched environments. These findings indicate that relatively simple and short‑term structural enrichment can enhance key foraging abilities in juvenile salmon, with potential implications for improving post‑release performance and survival of hatchery‑reared fish.