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与繁殖环境下尼罗罗非鱼（Nile tilapia）雌性个体的繁殖性能。本次研究共在巴西两处不同环境（分别为巴西巴拉那州马林加市的试验点1——容积10 m³的hapa养殖网箱，以及试验点2——容积1 m³的hapa养殖网箱）与巴西米纳斯吉拉斯州阿尔费纳斯市的一处环境（试验点3——容积14 m³与28 m³的hapa养殖网箱）中，对451尾雌性尼罗罗非鱼开展评估。试验对象按年龄划分为三组：1龄组（年龄<1年）、2龄组（年龄1~2年）以及3龄组（年龄>3年）。试验于2012年10月至2013年3月期间开展，每周对产卵情况进行一次核查，整个评估周期共计23周。统计分析采用SAS统计软件的Proc Genmod过程完成。针对2龄组个体，试验点2在多次产卵率、产卵频率以及单雌产卵量这三项指标上均低于其余试验点。同一试验点内，1龄组与2龄组的各项指标未检测到显著差异；但试验点3中的3龄组雌性个体的繁殖性能显著优于2龄组。研究结果表明，避免使用1 m³的单尾养殖网箱（hapa），并在亲鱼种群中保留老龄雌性个体，可有效提升尼罗罗非鱼的繁殖效果。