Studies on genetic variability of hatchery and wild populations of fishes by DNA markers

使用少量繁殖者生产孵化场饲养的幼鱼并将其释放到环境中的种群增强计划可能会对野生种群的遗传多样性产生负面影响，因为释放的种群的遗传可变性降低了。采用DNA多态性标记法，对红鲷（Pagrus major）野生种群和孵化场种群的遗传多样性进行了调查，并对不同种群的遗传变化进行了监测。构建了5套引物，分别对红鲷的微卫星位点和筛选多态性位点进行PCR扩增。遗传变异通过每个位点的平均等位基因数和平均杂合度来评价。孵化场群体的遗传变化主要表现在每个位点的平均等位基因数上，而不表现在平均杂合度上。这表明，这些遗传变化主要是由瓶颈效应引起的，而不是由遗传效应引起的。利用5个微卫星DNA标记，还追踪了育雏群及其系谱，以量化繁殖亲本的实际数量。然后，估算了有效贡献亲本数（Ne）和近交系数。结果表明，孵养鱼的平均观察杂合度（Ho=0.856）与亲鱼的遗传多样性（Ho=0.841）差异不显著（p < 0.05）。然而，在每个位点的等位基因数量和一些主要等位基因的频率上，两个种群之间存在显著差异（p<0.05）。超过73.5%的后代的系谱被有效地确定，至少91个育种者（250个）实际繁殖。估计Ne为63.7，近交系数小于0.78%。根据本研究所得的证据，讨论并提出了一种保存遗传变异和防止遗传变异丧失的方法。少

Stock enhancement programs that use a small number of breeders for the production of hatchery-reared juveniles to be released to the environment, may have negative effects on the genetic diversity of wild popurations due to a reduced genetic variability of the released stock. In this study, genetic diversity of wild and hatchery population of red sea bream (Pagrus major) was surveyed using DNA molymorphic markers to monitor genetic change in the brood stock and hatchery reared population. Five primer sets for PCR amplification were constructed for the microsatellite loci and the loci charcterized by screening polymorphism in red sea bream. The genetic variability was evaluated by average numbers of alleles per locus and mean heterozygosity. Distinct genetic changes in the hatchery populations were observed mainly in the average numbers of alleles per locus, but not in mean heterozygosity. This suggested that these genetic changes were mainly caused by bottle-neck effects and not by inb … More reeding. Brood stock and its pedigree were also traced, using five microsatellite DNA markers, to quantify the actual number of reproducing parents. Then, the effective number of contributing parents (Ne) and the inbreeding coefficient were estimated. It was found that the genetic diversity of the hatchery-reared stock in terms of the mean observed heterozygosity (Ho=0.856), was not significantly different (p>0.05) from that of the broodstock (Ho=0.841). However, significant differences (p<0.05) were found in the number of alleles per locus and in the frequencies of some major alleles between the two stocks. The pedigree of more than 73.5% of the progeny was effectively determined and at least 91 breeders (out of 250) actually reproduced. The estimated Ne was 63.7, consequently the estimated inbreeding coefficient was less than 0.78%. A way to conserve genetic variability and to prevent a loss of genetic variation in the hatchery-reared stock, were discussed and proposed based on the evidence obtained in this study. Less