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Masculinization of Nile tilapia ( Oreochromis niloticus ) by immersion in androgens

W.L. Gale·M.S. Fitzpatrick·M. Lucero·W.M. Contreras-Sanchez·C. B. Schreck
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Abstract

The use of all-male populations increases the efficiency and feasibility of tilapia aquaculture. The objective of this study was to determine the efficacy of a short-term immersion procedure for masculinizing Nile tilapia ( Oreochromis niloticus ). Two synthetic androgens were evaluated: 17α-methyldihydrotestosterone (MDHT) and 17α-methyltestosterone (MT). Exposure (3 h) on 10 and again on 13 days post-fertilization to MDHT at 500 μg/1 successfully masculinized fry in all experiments, resulting in 100, 94 and 83 ± 2% males in Experiments 1, 2 and 3, respectively. Immersions in MDHT or MT at 100 μg/1 resulted in significantly skewed sex ratios in Experiments 1 and 3 (MT resulted in 73 and 83 ± 3% males; and MDHT resulted in 72 and 91 ± 1% males) but not in Experiment 2. Immersion in MT at 500 μg/1 only caused masculinization in Experiment 3. Although further research and refinement is needed, immersion of Nile tilapia in MDHT may provide a practical alternative to the use of steroid-treated feed. Furthermore, when compared with current techniques for steroid-induced sex inversion of tilapia, short-term immersion reduces the period of time that workers are exposed to anabolic steroids.

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W.L. Gale, M.S. Fitzpatrick, M. Lucero, W.M. Contreras-Sanchez, C. B. Schreck. 1999. Masculinization of Nile tilapia ( Oreochromis niloticus ) by immersion in androgens. https://doi.org/10.1016/s0044-8486(99)00136-2

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