Associative learning, short-term memory, and colour preference during first feeding by juvenile Atlantic salmon

Abstract

The innate colour preference of 51 groups of 20 fry was examined at resorption of the visible yolk sac. A mixture of equal portions of blue, red, green, yellow, and unstained cod or capeling eggs were given to fry for 10-min feeding intervals after which fry stomach contents were examined and numbers of each colour of egg consumed were tabulated. Fry showed innate colour preference for red eggs; however, this could be changed to any other colour by only one previous feeding with eggs of the desired colour. This single-trial learning was retained up to 6 h after feeding but began to deteriorate after 21 h. Posisble applications in early rearing of Atlantic salmon fry in hatcheries are discussed.