Many Atlantic salmon Salmo salar populations in Europe are threatened by previous stocking with foreign hatchery strains. Temporal patterns of genetic characteristics of salmon from northern Spain, the southernmost European populations, were compared before and after species decline and heavy stocking with specimens from northern Europe. Eleven microsatellite loci were analysed in archival (scales from 1958−1960) and contemporary (2007−2008) samples from the River Sella. Temporal analyses revealed a similar heterozygosity between archival and contemporary samples, despite a drastic decrease in population abundance, while the contemporary sample showed a higher allelic richness due to the occurrence of foreign alleles. Considering only the alleles with at least 4% frequency in the archival sample, 2 alleles exclusive to the River Sella were absent in the contemporary sample, and 14 alleles showed a decrease of at least 4% frequency. Four alleles common in Scotland showed a high occurrence in the contemporary sample, so they are good candidates as markers of introgression of foreign genes. The heavy stocking with non-native Scottish broodstocks between 1970 and 1990 caused the introgression found in the contemporary sample when compared with the pristine population. An abrupt decrease was evident when the estimates of effective number of breeders were adjusted to take into account overlapping generations (NbAdj), effective population size (NeAdj) estimated from NbAdj, and number of breeders estimated using the sibship assignment method (NbSIB). The very low effective size values found in the contemporary sample, together with the detrimental synergy between genetic drift and high rates of introgression, represent a severe risk for the conservation of native salmon.

中文翻译：

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长期放养做法威胁到欧洲最南端大西洋鲑鱼鲑鱼种群的原始遗传多样性

欧洲的许多大西洋鲑鲑鱼种群受到先前放养外国孵化场菌株的威胁。将来自欧洲最南端的西班牙北部鲑鱼的遗传特征的时间模式与来自北欧的标本进行了物种衰退和大量放养前后的比较。在来自塞拉河的档案（1958-1960 年的规模）和当代（2007-2008 年）样本中分析了 11 个微卫星位点。尽管种群丰度急剧下降，但时间分析显示档案和当代样本之间存在类似的杂合性，而当代样本由于外来等位基因的出现而显示出更高的等位基因丰富度。仅考虑存档样本中频率至少为 4% 的等位基因，当代样本中不存在 2 个 Sella 河独有的等位基因，14 个等位基因显示出至少 4% 的频率下降。苏格兰常见的四个等位基因在当代样本中的出现率很高，因此它们是外源基因渗入标记的良好候选者。与原始种群相比，1970 年至 1990 年间大量放养非本地苏格兰亲虾导致在当代样本中发现基因渗入。当考虑到重叠世代 (NbAdj)、根据 NbAdj 估计的有效种群大小 (NeAdj) 以及使用同胞分配方法 (NbSIB) 估计的育种者数量进行调整后，育种者的有效数量估计值会突然下降。在当代样本中发现的有效尺寸值非常低，