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Factors affecting reproductive performance of tilapias of the Oreochromis genus in the lowland area of Trujillo state, Venezuela

Abstract:

A retrospective study was conducted in order to analyze the effect of year, season, month, genetic strain and the sex ratio on reproductive performance of tilapias of the Oreochromis genus from a fish farm located in Andrés Bello County of Trujillo State, Venezuela. Data were analyzed by logistic regression of SAS. The percentage of gravid tilapias was greater (P < 0.01) in the first (21.5%) than in the second (13.9%) year studied. Season affected reproductive performance, which was greater (P < 0.01) in the season 1 (24.4%) than in seasons 2 (15.0%) and 3 (12.7%). Grey tilapias (Oreochromis niloticus) were reproductively more actives than the red ones (Oreochromis spp) (21.5 versus 17.1%, respectively; P < 0.01). Sex ratio did not affect the three categories analyzed (17.1, 19.6 y 16.9% for sex ratios ≤ 1.5:1, > 1.5:1 ≤ 2.0:1 y > 2.0:1, respectively; P > 0.05). Two peaks of reproductive activity occurred throughout the year; one of greater magnitude during the first 4 months of the year and other markedly smaller during July to September. In conclusion, regardless of sex ratio, under the environmental and production conditions of the tilapia broodstock studied, spawning performance of females was greater during the dry period. Furthermore, tilapias from the Oreochromis niloticus strain were reproductively more active than those from Oreochromis spp group.