Morphometric characteristics, genetic profile, and histology of Nile tilapia in Mwenga Territory, South Kivu

This study assessed the morphometric diversity, genetic relationships, and histological profiles of Nile tilapia populations in Mwenga territory, South Kivu, an area affected by mining activities. A total of 144 specimens were collected from four subareas (Mwenga Centre, Kamituga, Kibe, and Kitutu) and analyzed at the Molecular Biology Laboratory of the Université Evangélique en Afrique. Analysis of 22 morphometric traits showed statistically significant variations (p < 0.05) among subareas, except for eye diameter, snout length, third anal spine length, longest anal ray, and post-orbital length, which did not exhibit significant differences. The heaviest fish were found in Kamituga (168.57 g), while the longest were in Kitutu (16.13 cm). Principal component analysis revealed three distinct clusters based on morphometric traits. Genetic analysis of 22 specimens using CO1 gene sequencing indicated moderate differentiation among subpopulations (Fst = 0.13) and low pairwise genetic distances, suggesting weak genetic divergence. Histopathological examination of selected tissues (flesh, liver, gills, fins, and heart) showed that flesh was the most affected tissue (35.62 %), with Kamituga exhibiting the highest hemosiderin deposits in muscle and liver, indicating potential heavy-metal contamination. These findings provide a valuable baseline for future genetic improvement and conservation strategies in the region.