Impacts of Invasive Aquatic Species on the Aquatic Ecosystem: A Case Study of Fish Spawning Areas in the Kafue Flat, Zambia

Abstract

Invasive alien species (IAS) are a major threat to global biodiversity and ecosystems, adversely affecting human wellbeing by disrupting essential goods and services. Zambia faces ecological challenges due to the unintended introduction of non-native fish species, such as Limnothrissa miodon, Oreochromis niloticus and Cherax quadricarinatus, primarily through unauthorised aquaculture. To determine the impact of invasive aquatic species, this study investigated the Kafue River and its associated Kafue Flats (Chunga and Blue Lagoons), critical water bodies known for their biodiversity and reliance on fish by local communities. Assessments were conducted along 1,200 meters of the Lower Kafue Basin using a mixed-methods approach, including fauna and flora sampling and socio-economic surveys. Results recorded 12 different aquatic plant species of which 6 were categories as invasive. Out of the 6, 3 invasive plants namely Aeschynomene flutans, Cyperus papyrus, and Cenchrus masainicus being predominant with a relative abundance of 60% vegetative cover in the study area. The study revealed no invasion Senecio vulgaris on the Blue Lagoon except for the Cenchrus masainicus with 52% dominant water surface cover. The area also hosts native fish species, including staple Catfishes and Tilapias. Results showed catches of invasion L. miodon 15% O. niloticus 10% and C. quadricarinatus 23% of total catch; indicating 33% increase that native species in Chunga Lagoon. Further, the result indicated no invasion of C. quadricarinatus in the Blue Lagoon. Socio-economic analysis highlighted fishing as a critical food and income source, especially during the dry season. Thus, the low fish species richness suggests moderate negative impacts of IAS on spawning grounds and indicating increased plankton productivity as a possible benefit. Future research should consider climate change, fishing practices, and human activities to further elucidate the dynamics of aquatic ecosystems.