All-male Tilapia Hybrids of Two Strains of Oreochromis niloticus |
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Authors: | Nilton G Marengoni Yoshio Onoue Tetsuo Oyama |
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Institution: | The United Graduated School of Agricultural Science, Kagoshima University, Faculty of Fisheries, 4–50–20 Shimoarata, Kagoshima 890 Japan; Kagoshima Freshwater Fisheries Experimental Station, 2699 Nishikata, lbusuki 891–03 Japan |
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Abstract: | Hybridization between Nile tilapia Oreochromis niloticus (Local and Stirling University strains) and blue tilapia O. aureus was found to be a tool to produce monosex populations. In order to select a purebred that produces all- or nearly all-male hybrids with high productivity, O. niloticus females and their diploid gynogenetics (meiogynes and mitogynes) were hybridized with O. aureus males. The sex ratio of progenies was evaluated from inter- and intraspecific crosses of two strains of Nile tilapia. Single-pair matings and group spawns under hatchery conditions showed no deviation ( P > 0.01) from the expected sex ratio of intraspecific crosses among two strains of Nile tilapia. However, a higher proportion of male progenies in blue tilapia was observed in group spawns in pond ( P < 0.004) and hatchery conditions ( P < 0.01). Only the Stirling strain and mitogynes produced all-male progenies under laboratory conditions. There were significant differences ( P < 0.05) in growth among hybrid progeny groups, when gynogens and their regular O. niloticus (Local strain) females were crossed with O. aureus males. Six-month hybrid offspring from mitogyne female parents grew better than those from regular and meiogyne female broods. |
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