Reproductive traits in different Nile tilapia genetic groups

ABSTRACT The aim of this study was to evaluate the reproductive traits of the non-inbred and inbred AquaAmérica, GIFT and AquaAmérica × GIFTgenetic groups. Six fish from each genetic group were used (2 females:1 male). Females were examined for the presence of eggs in their mouth at every four days, for 12 weeks. Reproduction occurred in all genetic groups (GIFT: 100%; non-inbred AquaAmérica and AquaAmérica ×GIFT: 75%; inbred AquaAmérica: 50%). Female weight, female standard length, total spawning weight, absolute fecundity, relative fecundity, spawn index and hatching rate did not differ significantly between the genetic groups. However, the non-inbred AquaAmérica variety showed lower values (P<0.05) for egg diameter (2.4mm) and egg weight (4.2mg) and higher values (P<0.05) for relative number of eggs (247.6 eggs/g of egg) than GIFT (egg diameter: 2.8mm; egg weight: 5.7mg; relative number of eggs: 175.4 eggs/g of egg) and AquaAmérica ×GIFT (egg diameter: 2.8mm; egg weight: 5.9mg; relative number of eggs: 168.8 eggs/g of egg). In conclusion, the non-inbred AquaAmérica variety produces smaller, lighter eggs but a higher relative number of eggs than the GIFT variety and the AquaAmérica ×GIFT cross; and inbreeding negatively affects spawning rate.

摘要 本研究旨在评估非近交与近交的AquaAmérica、吉富（GIFT）以及AquaAmérica×GIFT遗传群体的繁殖性状。本实验选取各遗传群体各6尾试验鱼，雌雄性比为2:1。连续12周每4天检查一次雌鱼口腔内是否含有鱼卵。所有遗传群体均成功实现繁殖：吉富群体繁殖率达100%；非近交AquaAmérica群体与AquaAmérica×GIFT杂交群体繁殖率为75%；近交AquaAmérica群体繁殖率为50%。雌鱼体重、雌鱼标准体长、总产卵重量、绝对繁殖力、相对繁殖力、产卵指数及孵化率在各遗传群体间均无显著差异。然而，相较于吉富群体（卵径：2.8mm；卵重：5.7mg；相对卵粒数：175.4粒/g卵）与AquaAmérica×GIFT杂交群体（卵径：2.8mm；卵重：5.9mg；相对卵粒数：168.8粒/g卵），非近交AquaAmérica品系的卵径（2.4mm）与卵重（4.2mg）更低（P<0.05），而相对卵粒数（247.6粒/g卵）更高（P<0.05）。综上所述，相较于吉富品系与AquaAmérica×GIFT杂交组合，非近交AquaAmérica品系所产鱼卵体积更小、重量更轻，但相对卵粒数更高；近交繁殖对产卵率存在负面影响。