Impact of Environmental Conditions on the Spawning Migration of Sea Trout (Salmo trutta L.) in Two Large, Sub‐Arctic River Systems

The global decline in salmonid stocks has increased the need for knowledge of local adaptations and life history strategies of salmonids. In this study, we used radio-telemetry tracking data from sea trout populations in two large high-latitude rivers to model upstream spawning migration speed of trout in response to prevailing environmental conditions and different stages of the migration. The results indicate that studied populations had similar responses to environmental changes, as trout inhabiting both rivers displayed similar responses to variation in discharge, temperature, and migrated distance covered. Higher discharge and temperature had a positive influence on trout migration speed, as did moderate discharge fluctuations. Migration distance influenced movements, as speed increased as trout moved upstream, while speed decreased late in the migration prior to spawning. These results highlight the adaptability of sea trout populations, underlining the importance of stock-specific information on habitat use and migration strategies for targeted management.