Reproduction performance of female Nile tilapia under different environments and age classes

The objective of this work was to verify the reproductive performance of females Nile tilapia in different age classes and reproductive environments. The data set was composed of 451 females evaluated in two different environments in Maringá, PR (hapas of 10 m3, place 1 and hapas of 1 m3, place 2) and in one environment in Alfenas, MG (place 3). The females were separated into three age classes, corresponding to animals with 1 (age 1), 2 (age 2), and 3 years old (age 3). The spawning verification was performed once a week in the period of October/2012 to March/2013, corresponding to 23 weeks of evaluation. The statistical analyses were performed using the Proc Genmod from the statistical program SAS. Place 2 showed the lowest results compared to the other places for multiple spawning, spawning frequency, and volume of eggs/female using animals of age 2. Statistical differences were not observed between ages 1 and 2 considering the same assessment place; however, the age 3 presented at the place 3 showed superior results than females of age 2. Therefore, avoid the use of animals in individual hapas and maintain older females in the squad can improve the reproductive results.Current assay verifies the reproductive performance of females of Nile tilapia in different age classes and reproductive environments. Four hundred and fifty-one females were evaluated in two different Brazilian environments, namely in Maringá, Paraná State, Brazil (Site 1 - hapas of 10 m3 and Site 2 - hapas of 1 m3) and in one environment in Alfenas, Minas Gerais State, Brazil (Site 3 – hapas of 14 and 28 m3). The females were divided into three age classes, corresponding to animals under one year (age 1); between one to two years (age 2); and over three years old (age 3). Spawning was verified once a week, from October 2012 to March 2013, corresponding to a 23-week assessment. The statistical analyses were performed with Proc Genmod from the statistical program SAS. Site 2 had the lowest results when compared to the other sites for multiple spawning, spawning frequency and volume of eggs/female for animals of age 2. Statistical differences were not detected between ages 1 and 2 for the same assessment site, although females at age 3 in Site 3 provided higher results than those at age 2. Results show that, precluding the use of animals in individual hapas (1 m³) and maintaining older females in the stock, may improve reproduction results.

Genotype by sex interaction at different phases during Nile tilapia culture period

ABSTRACT. Co(variance) components and genetic parameters were estimated for performance and morphometric traits in male and female Nile tilapia at different growth periods to verify the need for separate selection programs for the two genders. Data set contained information on 1,720 animals, collected in cage system. Two-trait analyses using Bayesian methodology were conducted and the records of males and females were considered distinct traits. Rates of additive genetic variance, phenotypic and heritability were higher for females in estimates for morphometric traits and higher for males in performance traits. Whereas common hatchery environment showed higher relative importance for males, the nursery caused greater variations in females. The reduction of the genetic correlation rates caused by growth increased the difference between genders and indicated the treatment of males and females as a distinct feature selection