Copadichromis chrysonotus is a zooplanktivorous cichlid member of the diverse fish
community inhabiting Lake Malawi's rocky, littoral habitat. Like most Lake Malawi cichlids,
this species' reproductive strategy is based on maternal mouthbrooding, but it is the only
littoral species known to spawn in the open water without a substrate-based territory.
This study investigated length at maturity, sexual dimorphism, spawning behaviour, breeding
seasonality, fecundity, fertility, egg size, and brooding habits of C. chrysonotus
in southern Lake Malawi. Males in breeding colouration aggregated in sheltered areas at
least several metres deep, and each male defended a mobile breeding territory near the
surface while attempting to attract females. Breeding was mostly continuous from August to
May, with peaks in August-September and January-March. A major lull in breeding activity
occurred in May and June. Mean fecundity and fertility increased significantly with female
total length, while mean egg length, mean egg mass and gonadosomatic index did not increase
significantly with female total length. Females brooded their young up to 15-16 mm total
length before abandoning them. Open-water spawning by C. chrysonotus may be an
adaptation to reduce both egg predation during spawning and competition for substrate-based
breeding territories.