The growth of Oreochromis andersoni (Pisces:Chichlidae) from the Okavango Delta, Botswana, and a comparison of the scale and otolith methods of ageing

Otoliths and scales were used for age and growth determination ofOreochromis andersonii from the Okavango Delta, Botswana. Marginal increment analysis showed that an annulus was formed in both the scales and otoliths during the dry summer period. Using scales, the growth ofO. andersonii was described by Lt = 285.27(1-e-0.26(t+2.02)) mm SL and using otoliths by the equation Lt = 267.48(1-e-0.25(t+2.18)) mm SL. Maximum age estimates of 10 years using scales and 13 years using otoliths were obtained and the growth curves were significantly different (p < 0.01). Age estimation using scales tended to over-emphasise growth inO. andersonii resulting in larger predicted lengths-at-age. For this reason, otoliths are considered to be more reliable and suitable than scales in determining the age and growth of this species.