The biology ofTilapia rendalliandOreochromis mossambicus(Pisces: Cichlidae) in a subtropical lake in Mozambique

This study of age and growth, reproduction and juvenile recruitment of Tilapia rendalli and Oreochromis mossambicus was undertaken in Lake Chicamba, a large, clear subtropical lake in central Mozambique. Sectioned otoliths were used to estimate age. Marginal zone analysis showed that annulus formation occurred during winter, in July and August. Maximum age estimates for T. rendalli and O. mossambicus were 16 and 10 years, respectively. Growth was described by the 3 parameter von Bertalanffy model as Lt = 238.74 (1-e-0,636(1 + 00905)) mm TL for T. rendalli and Lt = 266.06 (1-e-0 70904(1 + 0269)) mm TL for O. mossambicus. The length-at-50% maturity (Lm50) of male T. rendalli was 218 mm total lenglh (TL) and 205 mm TL in females. In O. mossambicus the L50 for males was 251 mm TL and for females 223 mm TL. Both species spawned throughout summer. Lake level was found to have no effect on spawning periodicity although recruitment was flood dependent.