DIFFERENTIAL PATTERNS OF FEEDING AND RESOURCE ACCUMULATION IN MATURING AND IMMATURE ATLANTIC SALMON, SALMO-SALAR

Maturing Atlantic salmon first accumulate nutrient reserves and then c ease feeding in the spring/summer prior to spawning. Here we examine p atterns 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 ma rked fish, and their feeding responses, weights, forklengths and body lipid levels were recorded, Maturing fish were larger and in better bo dy condition than non-maturing fish from October until July of the fol lowing year, They also had a greater motivation to feed than non-matur ing fish from April, The period of greatest differentials in growth ra te, body lipids and condition factor between the two groups of fish co incided with the period of differential feeding responses, The results are discussed with reference to the energetic requirements of maturat ion and breeding in Atlantic salmon, and the aquaculture implications of early differences in appetite of maturing and immature fish.