MATERNAL AGGRESSION DURING THE MOUTHBROODING CYCLE IN THE CICHLID FISH, OREOCHROMIS-MOSSAMBICUS

Maternal aggression was studied in Oreochromis mossambicus during the mouthbrooding cycle. Brooding females were observed in heterosexual ca ptive groups, and their agonistic interactions and behavioural activit ies were registered. Brooding females were classified into three class es according to the developmental stage of the brood they were incubat ing: phase 1, brooding eggs; phase 2, brooding fry with yolk-sac; phas e 3, brooding fry with exogeneous feeding. The behaviour of the broodi ng females was compared with the behaviour of control non-incubating f emales. During the brooding cycle females become increasingly more agg ressive toward other individuals, with their aggressiveness reaching a peak in phase 3. During the brooding cycle the females also suppress their feeding activities. The outcome of the agonistic interactions (v ictories-defeats) of the brooding females was positively correlated wi th the brooding phase but not with clutch size. The main function of m aternal aggression in O. mossambicus seems to be the defence of the vu lnerable brood against predators, including conspecifics, at a develop mental stage when the fry start to forage outside the mother's mouth. (C) 1998 Wiley-Liss, Inc.