Data from: Quantifying heritable variation in fitness-related traits of wild, farmed and hybrid Atlantic salmon families in a wild river environment

Farmed fish are typically genetically different from wild conspecifics. Escapees from fish farms may contribute one-way gene flow from farm to wild gene pools, which can depress population productivity, dilute local adaptations and disrupt coadapted gene complexes. Here, we reanalyse data from two experiments (McGinnity et al., 1997, 2003) where performance of Atlantic salmon (Salmo salar) progeny originating from experimental crosses between farm and wild parents (in three different cohorts) were measured in a natural stream under common garden conditions. Previous published analyses focussed on group-level differences but did not account for pedigree structure, as we do here using modern mixed-effect models. Offspring with one or two farm parents exhibited poorer survival in their first and second year of life compared with those with two wild parents and these group-level inferences were robust to excluding outlier families. Variation in performance among farm, hybrid and wild families was generally similar in magnitude. Farm offspring were generally larger at all life stages examined than wild offspring, but the differences were moderate (5–20%) and similar in magnitude in the wild versus hatchery environments. Quantitative genetic analyses conducted using a Bayesian framework revealed moderate heritability in juvenile fork length and mass and positive genetic correlations (>0.85) between these morphological traits. Our study confirms (using more rigorous statistical techniques) previous studies showing that offspring of wild fish invariably have higher fitness and contributes fresh insights into family-level variation in performance of farm, wild and hybrid Atlantic salmon families in the wild. It also adds to a small, but growing, number of studies that estimate key evolutionary parameters in wild salmonid populations. Such information is vital in modelling the impacts of introgression by escaped farm salmon.

养殖鱼类通常与野生同种个体（wild conspecifics）存在遗传差异。水产养殖逃逸个体可能促成从养殖种群到野生种群基因库（gene pools）的单向基因流（gene flow），这会降低种群生产力、稀释本地适应性（local adaptations）并破坏共适应基因复合体（coadapted gene complexes）。本文重新分析了两项实验的数据（McGinnity等，1997、2003）：该实验以养殖亲本与野生亲本经实验杂交获得的大西洋鲑（Salmo salar）后代为研究对象，共分为3个不同队列，在符合同质园实验条件（common garden conditions）的自然溪流中测定其生长表现。此前已发表的分析仅关注组间差异，未像本文一样利用现代混合效应模型（mixed-effect models）考量谱系结构（pedigree structure）。携带1个或2个养殖亲本的后代，在生命第1年与第2年的存活率均低于携带2个野生亲本的后代；且在排除异常家系（outlier families）后，该组间推断结果依然稳健。养殖组、杂交组与野生组家系间的表现差异幅度总体相似。在所有检测的生活史阶段，养殖组后代的体型通常大于野生组后代，但差异幅度中等（5%~20%），且在野生环境与孵化场环境中，该差异的幅度相近。基于贝叶斯框架（Bayesian framework）开展的定量遗传分析显示，幼体叉长（fork length）与体质量具有中等水平的遗传力（heritability），且这两个形态性状间存在较强的正遗传相关（genetic correlations，>0.85）。本研究采用更为严谨的统计方法，验证了此前研究得出的野生鱼类后代适合度（fitness）普遍更高的结论，并为养殖、野生及杂交大西洋鲑家系在野外的表现差异提供了家系水平的新见解。本研究还为数量虽少但正不断增长的、旨在估算野生鲑科（salmonid）种群关键进化参数的研究提供了补充数据。此类信息对于模拟逃逸养殖鲑的渐渗（introgression）效应至关重要。