橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）的选育效果评价

以橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）为基础群体，分别对其进行选育，并对产生的选育系F4代的选育效果进行了评价。经过4代的选育，橙色莫桑比克罗非鱼和荷那龙罗非鱼的日增重率分别比对照系提高了27．96％和36．73％，差异显著（P〈0．05），平均每代选育效应分别为6．99％和9．18％。F4代的体重变异系数分别为23．74％和22．17％，比对照组分别降低了24．83％和36．33％。而且第一次性成熟时这2种罗非鱼的平均体重都比对照系增加2倍以上，其杂交子代的雄性率达到了99．4％。试验结果表明，橙色莫桑比克罗非鱼和荷那龙罗非鱼的选育效果明显，F4代的生长性能有了显著提高，个体之间的生长速度趋于一致；也说明这2种罗非鱼F4代仍具有一定的选育潜力，对其继续进行选育是切实可行的。

Evaluation of selective breeding effect of Oreochromis mossambicus and O. hornorum at fourth generation

Selective breeding were performed on the base populations of Oreochromis mossambicus and O. hornorum respectively, and F4 generations were produced and evaluated. Compared with control group, the daily growth rate of F4 of O. mossambicus and O. hornorum was improved by 27.96% and 36. 73% （P 〈0. 05）, and the average selection response per generation was 6. 99% and 9. 18% , while variation coefficient of body weight was reduced by 24. 83% and 36.33% over the control group, respectively. At the first sex maturity, the mean body weight of the selected group F4 was increased more than two times of the control group respectively, and their hybrids [O. mossambicus ♀ （XX） × 0. hornorum ♂ （ZZ） ] had high and stable male rate. All these results showed that selection response of the two kinds of tilapia is remarkable, and the individual growth rate was turned to be consistent in the selected population. It also indicated that there are still some selection potentials in F4 generations, and it is feasible to proceed with selective breeding for growth of the two kinds of tilapia.