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

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.

本试验旨在探究不同年龄组尼罗罗非鱼（Nile tilapia）雌性个体在不同繁殖环境中的繁殖性能。试验共评估了451尾雌鱼，设置于巴西3个不同的试验环境中：其一为巴西巴拉那州马林加市的两处环境（站点1——10 m³哈帕网箱（hapa）、站点2——1 m³哈帕网箱）；其二为巴西米纳斯吉拉斯州阿尔费纳斯市的一处环境（站点3——14 m³与28 m³哈帕网箱）。供试雌鱼被划分为3个年龄组：1龄组（鱼龄不足1年）、2龄组（鱼龄1~2年）以及3龄组（鱼龄3年以上）。试验周期为2012年10月至2013年3月，期间每周开展一次产卵验证，总评估时长达23周。统计分析采用统计软件SAS的Proc Genmod模块完成。针对2龄雌鱼，在多次产卵率、产卵频率及单雌产卵量三项指标上，站点2的试验结果均显著低于其余两个站点。同一试验站点内，1龄与2龄雌鱼的繁殖指标未检测到显著差异；但站点3的3龄雌鱼繁殖性能显著优于2龄雌鱼。研究结果表明：规避在单个1 m³哈帕网箱中饲养雌鱼，并在亲鱼种群中保留老龄雌鱼，可有效改善尼罗罗非鱼的繁殖表现。