Establishment of hypoxia-tolerant F₃ generation of Megalobrama amblycephala and their growth performance under long-term hypoxia

On the basis of wild good broodstocks introduced from Poyang Lake (F₀ generation), the F₁ generation was obtained through population breeding from 2009 to 2011, and the passage from F₁ to F₂ was realized in 2011 through population breeding. In order to construct hypoxia tolerance strains of M. amblycephala, the Poyang Lake F₂ and " Pujiang No.1” F₉ broodstocks endured twice hypoxia stress in the summer and autumn in 2012, and 536 survival individuals were constructed as hypoxia-tolerant F₂ generation. In 2013, the F₂ parents (female 50, male 48) with great body weight and good body-shape were used to establish 24 F₃ family groups (22 groups of 2♀×2♂ and 2 groups of 3♀×2♂), a total of 100 F₃ families. The 100 F₃ families were cultured under hypoxia for one year from the 20th day post-hatching. By measuring the corresponding traits between growth and hypoxia tolerance, five fastest growing family groups (A2, A3, A18, A19 and A20) were selected; microsatellite analysis identified these rapidly growing individuals belonging to 20 families. Additionally, six faster growing groups (A4, A6, A17, A25, A27 and A28) belonging to 28 family were identified. Our results show that the growth performance of M. amblycephala was positively correlated with hypoxia-tolerance. Under long-time hypoxia stress culture at the first-year stage of F₃ families, the body weight of the families with strong hypoxia tolerance was significantly higher than that of the families with low hypoxia tolerance. The selected F₃ families with hypoxia resistant characteristics still maintained rapid growth rates at 2-year-old stage. The purpose of this study is to establish the hypoxia-tolerant F₃ generation for subsequent selection of new good breed of M. amblycephala.