ASSESSMENT OF FISH SPECIES COMPOSITION USING ENVIRONMENTAL DNA METABARCODING AND CATCH SURVEY IN THE SATELLITE LAKES OF LAKE VICTORIA, KENYA

Abstract

The satellite lakes of Lake Victoria are identified as key refugia for native fish species, most of which are threatened by factors such as invasive species and habitat loss. Nevertheless, fish species composition in these lakes are understudied, which drastically hampers fisheries management and conservation measures. This research applied both molecular (eDNA metabarcoding) and conventional methods through catch surveys to identify the fish species composition in Lakes Kanyaboli, Namboyo, Sare, and Bob. The morphometrics, DNA tissues, and questionnaire data were collected twice a month from November 2024 to February 2025. The Total Length (TL) and total weight (TW) of the fish were measured using a measuring board and an analytical balance, respectively. The eDNA and tissue samples were transported to SPYGEN Laboratory (France) for sequencing and bioinformatics analysis. A total of 95 fishermen were interviewed across the satellite lakes. 37.8% and 33.3% of fishermen in Kanyaboli and Bob, respectively, were in the age range of 30-39 years. The eDNA metabarcoding detected 31 taxa, while the catch survey recorded 21 taxa. Shannon Weiner diversity indices showed that Lakes Namboyo and Bob recorded the highest diversity, 1.64 and 1.43, respectively. Kanyaboli 1.3 and Lake Sare recorded the least diversity, 0.73, based on eDNA metabarcoding. Common species detected include the tilapiines, C. gariepinus, and P. aethiopicus. Two invasive species, Gambusia sp and Lates niloticus, and five haplochromine species (Pundamilia nyererei- found in all four lakes, Pundamilia pundamilia- found in all lakes except in Sare, Haplochromis maxillaris, Astatotilapia nubilus and Haplochromis argenteus were found in Kanyaboli. One-way Analysis of Variance (ANOVA) indicated significant differences between the total weight in all the lakes (p=0.001). The length-weight relationship of O. niloticus in Lakes Kanyaboli, Sare and Bob showed an isometric growth pattern (b=3), O. leucostictus and O. esculentus in Kanyaboli showed a negative allometric growth (b<3), O. leucostictus in Sare revealed a positive allometric growth (b=3.2), and O. variabilis in Sare had an isometric growth (b=3). Both C. gariepinus and P. aethiopicus across the four lakes showed a negative allometric growth with (b<3). The condition factor (K) and the Relative condition factor (Kn) were all above 1.0, indicating that the fish were in good condition across all the lakes. The study demonstrates the effectiveness of eDNA as a tool for fish biodiversity assessment in the satellite lakes. The findings will benefit fisheries officers, Researchers, policymakers and local communities by guiding conservation strategies and ensuring sustainable use of these aquatic ecosystems.