REGULATION OF HYPERPHAGIA IN RESPONSE TO VARYING ENERGY DEFICITS IN OVERWINTERING JUVENILE ATLANTIC SALMON

Resident juvenile Atlantic salmon responded to a period of winter food restriction by subsequently increasing appetite when food again becam e available. This hyperphagy contributed to the restoration of an ener gy deficit (derived from a biometric estimation of body lipid reserves ) incurred during the period of food restriction. The extent of this d eficit influenced the duration of the hyperphagic response: those fish incurring the greatest fat losses maintained appetite longer than tho se with a smaller energy deficit. The initial feeding intensity of fis h incurring a wide range of fat losses was found to be similar, indica ting that fish were regulating the length as opposed to the intensity of the hyperphagic response in order to restore losses. The ecological implications of the results are discussed in relation to juvenile sal mon overwintering strategies. (C) 1997 The Fisheries Society of the Br itish Isles.