Data from: Kokanee-sockeye salmon hybridization predominantly leads to a resident life history with outcomes for a long-term reintroduction program

<b>Abstract</b><br/><p>Stocking programs have been widely implemented to restore extirpated fish species to their historical ranges, and must include careful consideration of potential hybridization dynamics. The sockeye salmon (<em>Oncorhynchus nerka</em>) reintroduction project in Skaha Lake (British Columbia, Canada) provides an excellent opportunity to investigate the outcomes of hybridization between anadromous (migratory) sockeye and resident kokanee over a two-decade long program. Prior research established the presence of hybrids, with the vast majority of F1 spawners exhibiting a resident life history. Yet, it remains unknown whether anadromous hybrid smolts exhibit fitness effects in the form of reduced survival during migration, or whether they predominantly remain resident. Here, we paired cohort-based sampling (age-0 fry, age-1 smolts, adult spawners) in Skaha Lake with SNP genotyping, otolith microchemistry, and morphometrics to: 1) reconstruct trends in stock proportions of sockeye, kokanee and hybrids (F1, B1-sockeye, B1-kokanee) over a 15-year time series; and 2) investigate the morphological, behavioral and fitness outcomes of sockeye-kokanee hybridization. Genetic assignments revealed stock proportions varied widely over time and across cohorts, with hybrids making up a substantial proportion of the population despite earlier suggestions that hybrids may exhibit reduced fitness. Approximately 94% of F1 and 100% of B1-kokanee spawners exhibited microchemical evidence of a resident life history. Conversely, B1-sockeye spawners were evenly split between resident and anadromous, displaying a significant difference in fork length associated with life history and providing further evidence for a genetic basis to migratory behaviour. More broadly, our findings have important management implications for habitat restoration and underscore the need for continued monitoring with consistent sampling among partner organizations.</p>

摘要
红大麻哈鱼（sockeye salmon, *Oncorhynchus nerka*）重引入项目已被广泛用于将区域性灭绝的鱼类物种恢复至其历史分布范围，此类计划必须审慎考量潜在的杂交动态。加拿大不列颠哥伦比亚省斯哈湖的红大麻哈鱼重引入项目，为探究洄游型红大麻哈鱼与陆封型克奈尼鲑（kokanee）之间的杂交结果提供了绝佳契机——该项目已开展了二十年的跟踪研究。前期研究已证实杂交个体的存在，且绝大多数子一代（F1）产卵个体表现出陆封型生活史。然而目前仍不清楚：洄游型杂交降海幼鲑在洄游过程中是否存在存活率降低的适合度效应，或是它们是否主要保留陆封型生活史。
本研究结合斯哈湖的同龄群抽样（涵盖0龄仔鱼、1龄降海幼鲑与产卵成鱼）与单核苷酸多态性（SNP）基因分型、耳石微化学分析及形态测量学，旨在达成两个研究目标：1）基于15年的时间序列数据，重构红大麻哈鱼、克奈尼鲑及杂交个体（F1、回交红大麻哈鱼（B1-sockeye）、回交克奈尼鲑（B1-kokanee））的种群占比趋势；2）探究红大麻哈鱼与克奈尼鲑杂交的形态、行为及适合度结果。
遗传分型结果显示，种群占比随时间与同群群体差异显著，尽管此前有观点认为杂交个体适合度可能降低，但杂交个体在种群中占比可观。约94%的F1产卵个体与100%的B1-kokanee产卵个体，经耳石微化学分析证实为陆封型生活史。与之相反，B1-sockeye产卵个体在陆封型与洄游型之间分布均匀，且其叉长与生活史类型存在显著关联，这进一步为洄游行为的遗传基础提供了证据。
总体而言，本研究结果对栖息地修复的管理工作具有重要指导意义，同时也强调了合作机构间开展统一采样监测的必要性。