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

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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.