A successful population of largemouth bass, Micropterus salmoides, in a subtropical lake in Mozambique

Sectioned otoliths were used for age and growth determination of the alien Micropterus salmoides from Lake Chicamba, a hydroelectric dam in central Mo zambique. Marginal zone analysis showed that annulus formation occurred dur ing winter in August and September. The maximum estimated age was 5 years. Growth was described by the 3 parameter von Bertalanffy model as L-t = 465. 51 (1-e(-1.175(t+0.009))) mm FL. Juvenile growth rate was 23.1 mm per month during their first 7 months of life. The age at 100% maturity was 0.9 year s, and spawning occurred during August and September. The juvenile fish fed sequentially on the most abundant prey items. Spawning occured before any of the indigenous fish species and so, there is little inter-specific compe tition. Conspecific juveniles formed the most important constituent in the adult M. salmoides diet from October to December when alternative prey was limited. The total annual mortality rate (Z) for the species in Lake Chicam ba was 1.27 yr(-1), the mean empirical estimate of natural mortality (M) wa s 0.73 yr(-1), and fishing mortality (F) was calculated at 0.54 yr(-1). The success of M. salmoides in Lake Chicamba was attributed to limited inter-s pecific and intra-specific competition for prey as a consequence of the tim ing of the spawning, cannibalism and high mortality rates.