The age and growth of the greenhead tilapia Oreochromis macrochir (Pisces: Cichlidae) from the Okavango Delta, Botswana

Sectioned otoliths were used for age and growth determination of Oreochromis macrochir, a common cichlid species from the Okavango Delta, Botswana. The Okavango Delta is a vast inland wetland ecosystem which receives annual floodwaters from the highlands of southern Angola. Floodwaters reach the northern areas of the delta between January and March and the southern areas between June and September each year. Samples were collected from sites which receive flood waters between May and August. Marginal zone analysis showed that an annulus was formed between October and December during the dry, summer period. Maximum age estimates of eleven years were obtained and growth was described by the 3 parameter von Bertalanffy model as l sub(t) = 215.24(1-e super(-0.42(t+1.08))) mm SL.