Migration of wild and hatchery reared smolts of Atlantic salmon, Salmo salar L., through lakes

In 1982 and 1983 descending wild Atlantic salmon smolts, Salmo salar L., were caught in a fish‐trap at the mouth of the River Imsa. Together with hatchery‐reared smolts of the River Imsa strain they were tagged and released at three different sites of the Imsa‐Lutsi watercourse: in the Imsa River 1 km above the trap, and in two lakes, 3 and 11 km upstream of the trap. The recapture‐rate in the fish‐trap decreased with increased migration distance. The hatchery‐reared smolts migrated downstream faster than wild smolts. Lake‐released smolts were considerably delayed in their downstream migration compared to the river released smolts. The results are discussed in relation to environmental and physiological parameters.