Contribution assessment of hatchery origin black sea bream Acanthopagrus schlegeli into natural populations using microsatellite markers

利用6个微卫星DNA标记对日本大雄湾人工养殖的黑鲷的遗传多样性进行了连续两年的监测。每个位点的等位基因数为6 ~ 20个，平均等位基因数为0.83-0.88个。在所有样本中均观察到来自HWE的突变，表明两个后代组中杂合性过量，亲鱼和野生样本中杂合性不足。在2003年和2004年，分别有33.7%和38.5%的标本被确定为孵化场的起源，每年有另外40%的样本与单亲相匹配，这表明与自然种群的混合物。后代组提出了一个减少28.9%的等位基因的亲鱼两年的分析。组之间的同质性也证实了FST的低值，警告黑鲷栖息在大雄湾在较长的时间内，以避免可能的遗传漂变的监测的必要性。在本研究中获得的结果代表了一个明确的例子，尽管以前释放的青少年的高存活率;交配少数育种者可能会释放对遗传多样性的负面影响。这一经验证明，无论何时进行种群改良，都有必要估计和监测自然资源的遗传进化。

Genetic diversity of hatchery origin black sea bream (Acanthopagrus schlegeli) released at Daio Bay in Japan was monitored during two consecutive years using 6 microsatellite DNA markers. The number of alleles per locus ranged from 6 to 20 while Ho averaged 0.83-0.88 at all loci. Departures from HWE were observed in all samples, showing heterozygosity excess in both offspring groups and deficit in the broodstock and wild samples. The 33.7% and 38.5% of the specimens in 2003 and 2004, respectively ; were identified as hatchery origin, with another 40% of the samples matching with a single parent each year, suggesting admixture with the natural population. The offspring groups presented a reduction of 28.9% of the alleles regarding the broodstock for the two years analyzed. The homogeneity between groups was also confirmed by the low values of Fst, warning about the necessity of monitoring the genetic diversity of black sea bream inhabiting Daio Bay during longer periods in order to avoid possible genetic drifts. The results obtained in the present study represent a clear example of how despite the high survival rates of previously released juveniles ; mating small number of breeders may unleash negative impact on genetic diversity. This experience evidences the necessity of estimating and monitoring the genetic evolution on natural resources whenever stock enhancement practices are carried out.