Scale Loss and Survival in Smolts of Atlantic Salmon (<i>Salmo Salar</i>) after Turbin Passage

Abstract

Field data obtained from smolts of Atlantic salmon (Salmo salar) passed through an Ossberger crossflow turbine indicated that scale loss was greater (24% of the total scaled surface area) in fish that died during the first 48 h after passage than in fish that survived longer than 48 h (16% scale loss) or in controls (15%). Histopathoiogy of selected tissues from turbine-passed fish revealed an incidence of lesions in brain and muscle greater than that detected by gross necropsy. The sensitivity of histologic examination approximately doubled the detection of damage among fish that survived longer than 48 h. Laboratory experiments indicated that an average scale loss of 27% increased mortality in fish held in freshwater. This increased mortality occurred after longer periods (8 d) than in the field, and we suggest that physical damage other than scale loss contributed to earlier mortality in turbine-passed fish.