Swimming performance of wild and F1-hatchery-reared Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts

The swimming performance of wild and hatchery-reared smolts of two salmonid species was investigated. Wild Atlantic salmon smolts (WS) and brown trout smolts (WT) of equal size were caught in fish traps during migration. Hatchery-reared smolts of both species (HS and HT for salmon and trout respectively) were first generation offspring from wild broodstock. The swimming performance of individual smolts from the four groups (WS, HS, WT, HT) was tested three consecutive times using a swimming flume with water flowing at a start rate of 0.16 m.s(-1) and a constant acceleration rate of 0.167 cm.s(-2) (10 cm.s(-1).min(-1)). Wild caught smolts of both species performed significantly better than those reared in hatchery conditions. The WS group were observed to maintain an average swimming speed (U-burst) that was 30% faster than the HS group, whereas the wild trout smolts were superior to HT by approximately 25%. Repeated measures revealed species-specific exhaustion patterns. Brown trout smolts maintained consecutive U-burst indicating significant stamina compared with Atlantic salmon smolts that were found to be exhausted by the initial trial.