Due to their important adaptive potentialities, tilapia have colonised a wide range of habitats which could be related to their various reproductive strategies. Some traits of the reproductive cycle present a great plasticity and can be modulated by many environmental and/or social factors. We investigated some of them under controlled conditions in three tilapia species, Oreochromis niloticus, O. aureus and the red tilapia (Red Florida strain). At a constant temperature, a clear influence of a seasonal photoperiod is demonstrated on the reproductive activity of O. aureus. Under a typical tropical 12L:12D photoperiod, most reproductions occurred in the mid-afternoon (3 p.m.). Environmental complexity strongly stimulated the production; both reproductive activity and fry survival seemed to be stimulated by the presence of artificial shelters. The reproductive cycle of O. niloticus is characterised by the variability of its periodicity: vitellogenesis can be delayed or stimulated by the maternal behaviour as demonstrated by eggs/fry suppression or exchange experiments. In O. niloticus, O. aureus and the red tilapia, the reproductive activity of individually tagged male and female breeders has been investigated during long term periods (8-12 months) in tanks or race-ways. When seed were removed from incubating females at a 10 day interval, few males and females were involved in the overall fry production. Apparently, the other females only took part into spawning activity during the inter spawning period of the most active breeders. The individual characteristics of the clutches produced by these two types of females have been compared. The importance of social factors in the reproductive efficiency of tilapia species is discussed.