This study investigated factors influencing farmers’ choice of seed or broodstock sources and analyzed morphometric and genetic variation in farmed and wild Oreochromis niloticus (Nile tilapia) across Uganda’s agroecological zones (AEZs). Data were collected from 221 fish samples, sourced from 15 farms and four major lakes; through semi-structured farmer interviews, morphometric imaging, and fin clip sampling.
Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) were used to identify shape variation and population differentiation based on morphometric traits. Genetic variation was assessed by sequencing the mitochondrial DNA D-loop region, with genomic DNA extracted at Makerere University and sequencing conducted at NRF-SAIAB.
Results showed that 50% of farmers sourced seed from the Lake Victoria Crescent AEZ. Significant shape divergence was detected among populations for principal components 1 and 2 (P < 0.05). Genetic analysis revealed high haplotype diversity (Hd = 0.864) and low nucleotide diversity (π = 0.009), with phylogenetic analysis grouping populations into four distinct clusters.
The findings suggest that environmental differences across AEZs, particularly temperature, may drive both morphometric and genetic divergence; hence, influencing the growth and performance of O. niloticus in aquaculture systems. To ensure optimal productivity and minimize ecological risk, the study recommends regulating fish translocation and promoting the use of genetically and morphologically suited broodstock.
Key words: Nile tilapia, Agroecological zones, Morphometric variation, Genetic diversity and Aquaculture