A comparison of the otolith and scale methods of ageing, and the growth of Sarotherodon mossambicus (pisces:Gchlidae) in a Venda impoundment (Southern Africa)

Abstract

Otoliths and scales were used for age and growth determinations of Sarotherodon mossambicus in the LuphepheNwanedzi impoundment, a subtropical man-made reservoir in Venda, northern South Africa. Two rings are deposited annuallyon the otolith whereas only one ring Is deposited on the scales. Using otoliths the growth of S. mossambicus is described by L_t = 27,3 (1 - e ^{-0.425(1+0.299}) cm and using scales by L_t = 26,8 (1 _e^{-0.389(1+0.045)}) cm. These two curves differ Significantly (P<0.01)_ The adequacy of these curves was tested by means of Ford-Walford plots. It is postulated that otoliths provide a more reliable estimate of age and growth than scales in subtropical and temperate regions. Males grow faster than females. Based on otoliths the growth of male S. mossambicus in the Luphephe-Nwanedzi impoundment is described by L, = 27,0(1- e^{-0.417(1+0.504)}) cm SL and that of females by L, = 25,8(1-e ^{-0.370(1+0.497)}) cm SL. The growth of S. mossambicus in the Luphephe-Nwanedzi impoundment is compared to other S. mossambicus populations in South Africa.