Skaala Øystein, Besnier Francois, Borgstrøm Reidar, Barlaup BjørnTorgeir, Sørvik Anne Grete, Normann Eirik, Østebø Britt Iren, Hansen Michael Møller, Glover Kevin Alan
Institute of Marine Research Nordnes, Bergen Norway.
Faculty of Environmental Sciences and Natural Resource Management Ås Norway.
Evol Appl. 2019 Mar 6;12(5):1001-1016. doi: 10.1111/eva.12777. eCollection 2019 Jun.
Interactions between domesticated escapees and wild conspecifics represent a threat to the genetic integrity and fitness of native populations. For Atlantic salmon, the recurrent presence of large numbers of domesticated escapees in the wild makes it necessary to better understand their impacts on native populations. We planted 254,400 eggs from 75 families of domesticated, F1-hybrid, and wild salmon in a river containing up- and downstream traps. Additionally, 41,630 hatchery smolts of the same pedigrees were released into the river. Over 8 years, 6,669 out-migrating smolts and 356 returning adults were recaptured and identified to their families of origin with DNA. In comparison with wild salmon, domesticated fish had substantially lower egg to smolt survival (1.8% vs. 3.8% across cohorts), they migrated earlier in the year (11.8 days earlier across years), but they only displayed marginally larger smolt sizes and marginally lower smolt ages. Upon return to freshwater, domesticated salmon were substantially larger at age than wild salmon (2.4 vs. 2.0, 4.8 vs. 3.2, and 8.5 vs. 5.6 kg across sexes for 1, 2, and 3 sea-winter fish) and displayed substantially lower released smolt to adult survival (0.41% vs. 0.94% across releases). Overall, egg-to-returning adult survival ratios were 1:0.76:0.30 and 1:0.44:0.21 for wild:F1-hybrid:domesticated salmon, respectively, using two different types of data. This study represents the most updated and extensive analysis of domesticated, hybrid, and wild salmon in the wild and provides the first documentation of a clear genetic difference in the timing of smolt migration-an adaptive trait presumed to be linked with optimal timing of entry to seawater. We conclude that spawning and hybridization of domesticated escapees can lead to (i) reduced wild smolt output and therefore wild adult abundance, through resource competition in freshwater, (ii) reduced total adult abundance due to freshwater competition and reduced marine survival of domesticated salmon, and (iii) maladaptive changes in phenotypic traits.
养殖逃逸个体与野生同种个体之间的相互作用对本地种群的遗传完整性和适应性构成了威胁。对于大西洋鲑鱼而言，野外大量养殖逃逸个体的反复出现使得有必要更好地了解它们对本地种群的影响。我们在一条设有上下游陷阱的河流中投放了来自75个家系的养殖鲑鱼、F1杂交鲑鱼和野生鲑鱼的254,400枚鱼卵。此外，还向河中放流了41,630尾相同谱系的孵化场培育的幼鲑。在8年的时间里，共捕获了6,669尾洄游的幼鲑和356尾洄游的成年鲑鱼，并通过DNA鉴定出它们的原家系。与野生鲑鱼相比，养殖鱼的鱼卵到幼鲑的存活率显著较低（各群体分别为1.8%和3.8%），它们在一年中洄游得更早（多年平均提前11.8天），但幼鲑的体型仅略大，年龄略小。回到淡水区域后，养殖鲑鱼在成年时的体型比野生鲑鱼大得多（1龄、2龄和3龄越冬鱼的雌雄个体体重分别为2.4千克对2.0千克、4.8千克对3.2千克、8.5千克对5.6千克），且放流的幼鲑到成年的存活率显著较低（各放流批次分别为0.41%和0.94%）。总体而言，使用两种不同类型的数据，野生鲑鱼、F1杂交鲑鱼和养殖鲑鱼从鱼卵到洄游成年鲑鱼的存活率分别为1:0.76:0.30和1:0.44:0.21。这项研究代表了对野外养殖、杂交和野生鲑鱼的最新且广泛的分析，并首次记录了幼鲑洄游时间上明显的遗传差异——这是一种被认为与进入海水的最佳时间相关的适应性特征。我们得出结论，养殖逃逸个体的产卵和杂交可能导致：（i）由于淡水环境中的资源竞争，野生幼鲑产量减少以及野生成年鲑鱼数量减少；（ii）由于淡水竞争和养殖鲑鱼海洋存活率降低，成年鲑鱼总数减少；（iii）表型性状的适应不良变化。
