Fish diversity and composition of Tugwi Mukosi Dam, Zimbabwe's largest inland reservoir post impoundment

Abstract

AbstractThe fish diversity and composition of Tugwi Mukosi Dam, Zimbabwe's largest inland reservoir was investigated in 2019 (post impoundment phase) after the reservoir filled in 2017. The main objective of this study was to determine the status of the fish community in Zimbabwe's largest reservoir post dam impoundment. Nine species belonging to four families were observed from the reservoir. The Cichlidae family with the following species: Oreochromis niloticus, Oreochromis mossambicus, Tilapia rendalli, Oreochromis macrochir and Serranochromis thurmbergi constituted 66.7% of the sample, the Centrarchidae with species Micropterus salmoides constituted 12.7% of the sample and the Cyprinidae family with species Labeo cylindricus constituted 2.7% of the sample, which was the least abundant. The O. niloticus population, which was introduced in 2017, seemed to have reached the establishment stage’ on the introduction–naturalisation–invasion continuum as evidenced by its ability to survive and breed. Oreochromis mossambicus, which formerly dominated the riverine catches, appeared to be still dominant in the new environment. Micropterus salmoides, O. niloticus and O. mossambicus had active ripe and ripe‐running individuals throughout the year whereas O. macrochir, S. thumbergi and L. cylindricus had no clear trend in terms of breeding. The growth performance indices for O. mossambicus, M. salmoides and O. niloticus ranged from 5.03 to 5.36. The highest mortality rate was 2.81 for M. salmoides and the lowest was 1.35 for O. mossambicus. There is no pre‐impoundment data for the fish community and abundance in Tugwi Mukosi Dam and therefore these results provide baseline data 3 years after impoundment. These results are a benchmark for future studies and new insights into the fish communities of large reservoirs. Future fish studies in Tugwi Mukosi should investigate how this fish community continues to evolve over time.