AGE AND GROWTH OF LABEO UMBRATUS (PISCES: CYPRINIDAE) IN LAKE LE ROUX ON THE ORANGE RIVER, SOUTH AFRICA

Abstract

Age, growth and relative body condition of Labeo umbratus in Lake le Roux were investigated from samples collected from 1979 to 1982. Annuli are formed once a year on the scales and otoliths as growth commences in spring or early summer. Growth rates show large interseasonal variations which can be related to water transparency, but asymptotic length appears to be independent of previous growth history. When compared to other populations of this species the relative body condition is low and declines sharply as water transparency decreases. Year class strength did not show large interannular fluctuations, indicating that feeding areas in this relatively deep reservoir may limit abundance.