Assessment of Scale-loss to Atlantic Salmon (salmo Salar L.) Smolts from Passage through an Archimedean Screw Turbine

The potential for external damage to Atlantic salmon (Salmo salar L.) smolts from passage through an Archimedean screw turbine was tested with controlled field trials at two turbine speeds. Change in external condition of smolts was measured by grading photographs of individual fish for scale-loss before and after the tests. Results were compared between turbine-passed and control smolts. There were no significant differences in proportions of fish with new scale-loss between treatment and control smolts. New scale-loss of between 4 and 30% was seen in 7.46% of turbine-passed smolts, exceeding the prevalence in control smolts by 2.46%. Of these, 1.49% had minor scale-loss of 5-9%. Minor scale-loss was more prevalent for both groups at the faster turbine speed, although differences between treatment and control groups were more apparent at the slower speed.