An Investigation of Fish Species Diversity, Abundance and Diets of Selected Predator Fish in Insukamini Dam, Zimbabwe

Abstract

A total of 8 fish species (n=465) were caught by gill nets from December 2009 to May 2010 to investigate fish ecology in Insukamini dam. The species were identified as: Serranochromis robustus (n=18), Micropterus salmoides (n=36), Clarias gariepinus (n=72), Oreochromis mortimeri (n=192), Oreochromis macrochir (n=27), Tilapia rendalli (57), Tilapia sparrmanii (n=6) and Oreochromis niloticus (n=57). The largest catches of fish were recorded in February (n=210). O. mortimeri reported the most abundant fish species of 41.29 %. The least abundant fish species of 1.29 % was found in T. sparrmanni. C. gariepinus had the highest mean standard length and weight of 40 cm (ranged from 31.5 to 51.0 cm) and 1082.8 g (ranged from 506 to 1 220 g) respectively. T. Rendalli showed the lowest mean standard length and weight of 16.4 cm (ranged from 12.4 to 25.0 cm) and 215.8 g (ranged from 180 to 350 g) respectively. The diets of S. robustus, M. salmoides and C. gariepinus comprised of fish, snails, insects and worms. Fish were the most dominant food for the predators accounting for 94 % of the stomach contains in M. salmoides. The stomach of C. gariepinus contained 78.8 % unidentified digested material while S. robustus had 11.8 % empty stomachs. The total numbers and sizes of fish caught were mainly affected by predation, poaching, inter- and intra-specific competition and gill nets of the same inch size that were used.