Assessing the Potential Presence and Impact of Nile tilapia, Oreochromis niloticus (Pisces: Cichlidae; Linnaeus 1758) in Mutukutuku Reservoir in Solwezi, Zambia

Abstract

Invasive alien species are one of the greatest threats to biodiversity and ecosystem globally, affecting delivery of ecosystem goods and services, and consequently human well-being. Oreochromis niloticus is one of the most highly successful invaders of aquatic ecosystems with competitive characteristic advantages over indigenous species. The aim of this study was to investigate the potential presence and impact of O. niloticus on Mitukutuku fishery. The study was undertaken using fisheries independent surveys for the period of 2 months. Fish identification key and gel electrophoresis identification methods were also used to confirm presence of O. niloticus and also possible hybridization with indigenous congeneric species. Fisheries dependent survey was conducted with fishers and traders to further assess presence of the invasive species and its impacts on their catches and socio-economic well-being. A total of 32 Oreochromis hybrids species and 19 of O. niloticus were found in the reservoir. This confirmed a higher proportion of O. niloticus in the reservoir. Results from interviews of fishers and traders revealed catch per unit effort of O. hybrids and O. niloticus to be higher compared to that of indigenous congeneric species. Similarly, fish traders confirmed that income for the fish sales increased from 5% in March to 7% in August. Overall, these results suggested that O. niloticus does not only exist in Mitukutuku reservoir, but also hybridizes with native species and dominates the entire stretch of the reservoir threatening loss of biodiversity and aquaculture breeding programme. There is need for restricting culture of O. niloticus in Zambia.