Differential patterns of feeding and resource accumulation in maturing and immature Atlantic salmon, Salmo salar

Maturing Atlantic salmon first accumulate nutrient reserves and then cease feeding in the spring/summer prior to spawning. Here we examine patterns of feeding behaviour and reserve accumulation in maturing and immature fish of the same age from the onset of the maturation cycle (autumn) to the onset of anorexia (summer). Two hundred one-sea-winter fish were sampled monthly from sea cage populations of individually marked fish, and their feeding responses, weights, forklengths and body lipid levels were recorded, Maturing fish were larger and in better body condition than non-maturing fish from October until July of the following year, They also had a greater motivation to feed than non-maturing fish from April, The period of greatest differentials in growth rate, body lipids and condition factor between the two groups of fish coincided with the period of differential feeding responses, The results are discussed with reference to the energetic requirements of maturation and breeding in Atlantic salmon, and the aquaculture implications of early differences in appetite of maturing and immature fish.