Nile Tilapia (Oreochromis niloticus) is a vital aquaculture species in Kenya, contributing significantly to food security and economic development. However, reduced genetic diversity and inbreeding depression have led to suboptimal growth performance and productivity in farmed stocks. This study explores the impact of selective breeding on genetic enhancement and productivity improvement in farmed tilapia populations. Through a structured breeding program incorporating genetic assessments, controlled breeding strategies, and performance evaluations, we aim to enhance growth rates, disease resistance, and adaptability to local aquaculture conditions. Both on-farm growth trials and molecular approaches were used to validate the impact of selection on the Sagana Strain. Sagana strain (SAG-F8) produced through selective breeding, super YY strain (KAM YY) from Kamuthanga fish farm and the local strain (LOC-T) obtained from Siaya county were exposed to growth performance trials. The fish were fed 35% crude protein diet for 180 days at Bukani Aquapark. For molecular approaches, Polymerase chain reaction (PCR) was used to amplify DNA with nine microsatellite DNA markers designed for O. niloticus. Genetic diversity was quantified using several different parameters, including the average number of alleles per locus (A), the total number of alleles per population (NA), the number of effective alleles per population (AE), allelic richness (AR), observed heterozygosity (HO), expected heterozygosity or gene diversity (HE), and fixation index (FST).
There was no significant difference in terms of mean weight gain (MWG) between SAG- F8 and LOC-T strain exhibiting 159.786±6.76 g and 158.623±4.67 respectively. However, under similar conditions, the KAM-YY strain had a significantly lower MWG compared to the two strains. Food conversion ratio (FCR), specific growth rate (SGR) did no demonstrate any significant difference amongst the different strains. The trend is confirmed in genetic diversity assessment results where, the Sagana strain exhibited a higher genetic variability than all the other farmed strains. The highest allele richness was observed in fish samples from KMFRI Sagana Centre, with a mean of 7.625 alleles per locus, the lowest Hₒ was recorded in the Victory Farm population (0.625). The findings underscore the importance of genetic management in aquaculture and provide a roadmap for implementing large-scale breeding programs to enhance the resilience and productivity of tilapia farming in Kenya.
Keywords: Selective breeding, genetic diversity, tilapia, aquaculture, productivity, Oreochromis. niloticus