Effects of Year, Species and Rearing Environment on Synthetic and Androgen Efficacy for Sex Reversal in Nile and Blue Tilapia

Abstract

Monosex, all-male tilapia culture can improve production efficiency by preventing uncontrolled reproduction and associated growth losses. This study evaluated the effects of masculinising treatment, species, rearing environment, and production year on sex-reversal success in Nile tilapia (Oreochromis niloticus) and blue tilapia (Oreochromis aureus). A retrospective four-year dataset (2020–2023) comprised 1,200 fries distributed across two species, two rearing environments, and three treatments: 17α-methyltestosterone (MT), honey, and goat testis extract (GTE). Reversal proportions were assessed using descriptive statistics, Pearson chi-square tests, pairwise two-proportion z-tests, and multivariable binomial logistic regression. MT produced the highest reversal rate (80.0%), compared with honey (64.0%) and GTE (58.0%), and the treatment effect was significant (χ² = 47.04, p < .001). The controlled pond culture environment produced a higher reversal rate than the open field pond (74.0% versus 60.7%; χ² = 23.65, p < .001). The difference between O. aureus and O. niloticus was marginal (70.0% versus 64.7%; p = .056), while outcomes were identical across the four production years. Logistic regression identified MT (OR = 2.97) and controlled rearing (OR = 1.90) as significant independent predictors. A significant treatment × environment interaction indicated that the advantage of MT was greatest under controlled conditions. Honey and GTE achieved lower but measurable masculinisation, warranting further assessment under standardised conditions.