A study of the ichthyofauna of a small tropical reservoir, south-eastern lowveld, Zimbabwe

Abstract

Fish diversity in Malilangwe Reservoir in the south-eastern lowveld of Zimbabwe was investigated in 2011 to determine the community structure. The aim of this study was to determine the current status of an artificial fish community in a small reservoir that does not normally overflow and to assess how the fish have adapted to this environment. Eight species belonging to five families were collected from the reservoir. The cichlids Oreochromis mossambicus, O. macrochir, O. placidus and Tilapia rendalli made up 46% by number of the sample, the cyprinid Labeo altivelis made up 40% of the sample, and T. rendalli, the least numerous species, made up 0.2% of the sample. The population of T. rendalli seemed to be depleted, whereas largemouth bass Micropterus salmoides, which were formerly numerous, appeared to be absent. Oreochromis placidus bred throughout the study period, whereas Clarias gariepinus, Hydrocynus vittatus, L. altivelis, O. macrochir and O. mossambicus showed an apparent lack of recruitment between July and August 2011. The growth performances of C. gariepinus, O. mossambicus, O. macrochir and O. placidus were assessed by means of the growth performance index (φ′) with values ranging from 3.10 to 3.41. The rates of total mortality (Z) were estimated for four species; the highest rate was 5.64 for O. placidus and the lowest was 1.17 for C. gariepinus.