The effect of illumination on alevins of Atlantic salmon (Salmo salar) and rainbow trout (S. gairdneri), incubated on different substrates

Atlantic salmon (Salmo salar) and rainbow trout (S. gairdneri) eggs were incubated in plexi-glass aquariums. After hatching, alevins were kept in darkness, two groups of each species without substrate, two groups in gravel and two groups in Astroturf artificial substrate. Every three days after hatching, heartfrequencies or respirationrates were counted as measure of different activity and stress in the various groups, following a 10 minutes exposure to light. The respiration rate and heartbeat frequence of Atlantic salmon alevins was generally lowered among all the groups, during the period of observation. The alevins reared in Astroturf, showed however the lowest and most stable respiration rate and heartbeat frequence, due to their low activity at the bottom of the aquariums