Age, growth rate and size at sexual maturity of Labeobarbus aeneus (Teleostei: Cyprinidae) in the middle Vaal River, South Africa

Age structure, growth and size at sexual maturity of smallmouth yellowfish, Labeobarbus aeneus (Burchell), were assessed in 2008-2009. Despite its angling and food importance, little has been published on many aspects of its ecology and biology, specifically its age structure in the Vaal River system. Of 193 L. aeneus collected by gillnetting, 96 were assessed for sexual maturity, and ages were estimated using scales (n = 143) and whole otoliths (n = 167). Whole otoliths were found to be the most appropriate method for ageing. Both males and females were present in all age classes, which ranged from 2 to 19 years. Males may live longer (maximum 19 years) than females (maximum 16 years). Fish matured relatively late in life, the males at 3 years and females at 5 years, corresponding to lengths of 254 and 375 mm FL, respectively. Growth was shown to be fairly slow, as asymptotic growth was reached only at 8 years.