ABSTRACT: The escape of domesticated Atlantic salmon Salmo salar from aquaculture facilities represents a continued threat to the genetic and demographic stability of wild salmon stocks. Escaped farm-origin salmon have been shown to hybridize with wild conspecifics, yet the long-term genetic impacts are generally unknown. Theoretically, life history variation, specifically precocial maturation of male hybrids, could fast-track introgression, but evidence for this has been sparse. Here, we used empirical and experimental data to examine the role of precocious male maturation in introgression. We examined hybrid class composition using juvenile sampling and genetic assignment over a 5 yr period following an escape event in southern Newfoundland, a region with high rates of natural male precocial maturation. Initially following the escape, the proportion of first-generation (F1) hybrids was high and then decreased annually, contrasting the proportion of backcross wild individuals, which increased over time. The presence and temporal distribution of backcross wild individuals supports the hypothesis that high rates of precocial maturation can fast-track the long-term impacts of escaped farmed salmon on wild populations via interbreeding. This was experimentally tested using lab-created wild, farmed, and F1 parr released and recaptured from a Newfoundland river to assess levels of precocious male maturation. Observed rates of maturation of F1 hybrids were high and similar to wild parr (77 vs. 73%, respectively), indicating that most F1 hybrids mature precocially. Our results suggest that rates of precocial male maturation should be explicitly considered in risk assessments evaluating the genetic impacts of escaped farmed salmon on wild populations.

中文翻译：

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雄性早熟有助于养殖大西洋鲑鱼渗入野生种群

摘要：驯化的大西洋鲑鱼Salmo salar的逃逸水产养殖设施对野生鲑鱼种群的遗传和人口稳定性构成持续威胁。已证明逃逸的农场鲑鱼与野生同种动物杂交，但长期的遗传影响通常是未知的。从理论上讲，生活史的变化，特别是雄性杂交种的早熟，可以加快基因渗入，但是这方面的证据很少。在这里，我们使用经验和实验数据来检验男性早熟在基因渗入中的作用。在纽芬兰南部发生逃跑事件后，我们在 5 年内使用青少年抽样和遗传分配检查了混合类组成，该地区自然男性早熟成熟率很高。最初在逃跑之后，第一代（F1）杂种的比例很高，然后逐年下降，而回交野生个体的比例随着时间的推移而增加。回交野生个体的存在和时间分布支持这样的假设，即高早熟率可以通过杂交快速追踪逃逸养殖鲑鱼对野生种群的长期影响。这是使用实验室创造的野生、养殖和从纽芬兰河释放和重新捕获的 F1 parr 进行的实验测试，以评估雄性早熟的水平。观察到的 F1 杂种的成熟率很高，与野生 parr 相似（分别为 77% 和 73%），表明大多数 F1 杂种早熟成熟。