The biology of Tilapia rendalli and Oreochromis mossambicus (Pisces : Cichlidae) in a subtropical lake in Mozambique

This study of age and growth, reproduction and juvenile recruitment of Tila pia rendalli and Oreochromis mossambicus was undertaken in Lake Chicamba, a large. clear subtropical lake in central Mozambique. Sectioned otoliths we re used to estimate age. Marginal zone analysis showed that annulus formati on 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 L-t = 238.74 (1-e(-0 .636(t + 0.905))) mm TL for T. rendalli and L-t = 266.06 (1-e(-0.7904(t + 0 .269))) mm TL for O. mossambicus. The length-at-50% maturity (Lm(50)) of ma le T. rendalli was 218 mm total length (TL) and 205 mm TL in females. In 0, mossambicus the Lm,, for males was 251 mm TL and for females 223 mm TL. Bo th species spawned throughout summer. Lake level was found to have no effec t on spawning periodicity although recruitment was flood dependent.