团头鲂双向选育效应研究

报道１９８６￣１９９９年团头鲂正向选育和逆向选育的两种截然不同的效果。正向选育采用混合选育法，每代从鱼苗到亲鱼的总选择率约为万分之四，选留健壮的较大个体，第五代成鱼阶段的平均日增重率比对照系（原种）提高２９．１％，即选育效应每代平均为＋５．８％。逆向选育为全兄妹近交，后代随机留养，近交系第三代成鱼阶段的平均日增重率比对照系（原种）降低１６．６％，即选育效应每代平均为－５．５％；近交系每第四代当年苗种阶段畸形率高达２．８％，越冬成活率比对照系低２８．４％，比选育系低４８．３％；选育系的越冬成活率比对照系提高３８．４％。本研究证明，科学的良性选育可大大提高养殖性能；近亲交配可导致养殖性能的迅速降低，必须严加防范。

Two-way selective response of Megalobrama amblycephala

This paper reports the completely different results of positive selective breeding and negative selective breeding of blunt snout bream , Megalobrama amblycephala in 14 years. The positive selective breeding is by mass selection, the total selective intensity from fry to brooder was about 0.04%. Large and healthy individuals were selected, the average daily body weight growth rate of selective strain F5 was 29.1% higher than the control group, e.g., 5.8% selective response per generation. The negative selective breeding is by full sib matting, which offsprings are kept randomly. The average daily body weight growth rate of adult fish of the 3th generation of inbreeding group was 16.6% lower than the control group, e.g.,-5.5% selective response per generation. In the 4th generation of inbreeding group, the deformity rate of fingerlings was 2.8%, survival rate overwintering was 28.4% lower than the control group, and 48.3% lower than the positive selective group.This study proved that the aquaculture performance can be improved significantly by scientific selection,but depressed rapidly by inbreeding,which should be prevented strictly.