Wild and Naturalized Hatchery Brown Trout: A Comparison of Movement, Space Use, and Survival in a Large Lake

ABSTRACT Most research comparing wild and hatchery‐produced fish focuses on recently stocked individuals. As a result, these studies only investigate the behavior of naive hatchery fish, leaving a knowledge gap regarding long‐term survivors. We compared the movement, space use, and survival of wild and hatchery‐reared brown trout ( Salmo trutta ) that had survived for multiple years in a large Swedish lake (345 km 2 ). Acoustic tracking of 38 wild and 56 naturalized, hatchery‐origin trout over 4 years revealed similar weekly travel distances, sub‐basin transitions, and survival rates between the groups. However, wild trout exhibited greater seasonal variability in their movement and sub‐basin usage than their hatchery‐reared conspecifics. These differences may reflect a reduced ability of hatchery trout to respond to environmental cues (e.g., prey availability). Our findings highlight that while hatchery‐reared trout can persist in the wild, behavioral differences may influence their local ecological interactions and long‐term fitness.