Feeding behaviour of fast- and slow-growing strains of rainbow trout, Oncorhynchus mykiss (Walbaum), during first feeding

The development of feeding behaviour in two rainbow trout strains and their hybrid was compared at the transition from endogenous nutrition to exogeno us feeding. After 60 min of acclimatization, the swimming pattern, spatial distribution, agonistic behaviour and snapping of fish were quantified by m aking 5-min observations on groups of five fish. Behavioural patterns were recorded in four replicate groups per treatment, before and after the intro duction of dry trout feed or Artemia nauplii (actometric tests) or extracts of these (olfactometric tests). Fish of the slow growing strain were less active than those of the other two strains. Greater swimming activity obser ved in the fish of the fast growing strain was associated with more rapid f eeding and a higher number of snapping responses. Such behavioural precocit y is of interest because it could provide the basis for the growth differen ces between the fast and slow growing strains.