Adult summer-run steelhead Oncorhynchus mykiss overwinter in freshwater for several months prior to spawning. In systems supporting mixed populations of fisheries and conservation importance, understanding the distribution and survival of pre- and postspawn fish is necessary for informed management. The upper Columbia River supports hatchery-origin components valued by anglers, natural-origin components of conservation concern, and temporary strays from downstream populations. We used radiotelemetry and PIT telemetry to monitor the behavior, distribution, and survival of adult steelhead during fall, overwintering, spawning, and postspawn periods, with a focus on use of the main stem versus four major tributaries. Adult steelhead (N = 807) were tagged at Priest Rapids Dam in 2015 and 2016. One-fifth of steelhead fell back below Priest Rapids Dam and did not reascend. A slight majority of tagged steelhead that overwintered upstream of Priest Rapids Dam did so in main-stem reservoirs (54%; N = 548). Overwintering in the main-stem Columbia River was more likely for later-arriving steelhead and was concentrated in the upstream-most reservoir. Winter tributary use was highest in the Wenatchee (26%; 2016) and Methow (18%; 2015) rivers, whereas no steelhead overwintered in the Entiat River. Harvest of hatchery-origin steelhead was 18% in 2015 and was near zero in 2016, when the fishery was suspended due to low adult returns. After accounting for reported harvest, annual overwinter survival did not differ between main-stem and tributary habitats, and relatively low adjusted survival of hatchery-origin steelhead in 2015 suggested unreported harvest. In contrast to low iteroparity rates (<3%), the majority of postspawn steelhead (56.5%) exited tributaries as kelts; kelt survival to Bonneville Dam was 65% in 2016 and 23% in 2017. Collectively, the results highlight the importance of understanding patterns of habitat use and mortality in steelhead populations when managers are faced with balancing harvest and conservation goals.

中文翻译：

---

上哥伦比亚河流域Steelhead越冬分布及产卵后存活

夏季运行的成年钢头Oncorhynchus mykiss在产卵前在淡水中过冬几个月。在支持渔业混合种群和保护重要性的系统中，了解产前和产后鱼类的分布和存活对于知情管理是必要的。哥伦比亚河上游支持垂钓者重视的孵化场来源成分、保护问题的自然来源成分以及下游种群的临时流浪。我们使用无线电遥测和 PIT 遥测来监测成鱼在秋季、越冬、产卵和产后期间的行为、分布和存活，重点是使用主干与四个主要支流。成年钢头（N = 807) 在 2015 年和 2016 年在 Priest Rapids Dam 被标记。五分之一的钢头落回 Priest Rapids Dam 之下并且没有重新上升。在 Priest Rapids 大坝上游越冬的标记钢头中的一小部分是在主干水库中越冬（54%；N = 548）。在主干哥伦比亚河越冬，较晚到达的钢头鱼更有可能越冬，并且集中在最上游的水库。冬季支流使用在韦纳奇 (26%; 2016) 和 Methow (18%; 2015) 河流中最高，而在恩蒂亚特河中没有铁头鱼越冬。2015 年孵化场来源的硬头鱼的收获率为 18%，2016 年接近于零，当时渔业因成鱼回报率低而暂停。考虑到报告的收获后，主干和支流栖息地的年度越冬存活率没有差异，2015 年孵化场来源的钢头鱼的调整后存活率相对较低表明未报告收获。与低迭代率（<3%）相反，大多数产后钢头鱼（56.5%）作为 kelts 离开支流；2016 年，Bonneville Dam 的 kelt 存活率为 65%，2017 年为 23%。