ObjectiveDespite decades of restoration work, Chinook Salmon Oncorhynchus tshawytscha in the Pacific Northwest remain under the protection of the U.S. Endangered Species Act (ESA). Chinook Salmon in the Skagit River basin play a vital role in the abundance and recovery of the Puget Sound Chinook Salmon Evolutionarily Significant Unit, which is currently listed as threatened under the ESA. The stream‐type juvenile (STJ) life history pattern of Chinook Salmon in the Skagit River has higher ocean survival to the adult stage (i.e., productivity) than that of parr or fry out‐migrants, and improvement in STJ Chinook Salmon habitat could increase abundance and diversity in the Skagit River basin. Our objective was to provide recommended ranges of variables shown to influence habitat selection in floodplains by STJ Chinook Salmon.MethodsUsing field observations from 70 sites within the Skagit River basin, we developed generalized linear mixed‐effects models across three seasons in floodplain habitats to correlate variable ranges with densities of STJ Chinook Salmon.ResultModel accuracy varied by season (summer: R2 = 0.24; winter: R2 = 0.56; spring: R2 = 0.54), and significant parameters included velocity, substrate, depth range, and distance to the closest connection with the main stem. Additional significant factors included wood cover, maximum water temperature, velocity range, and interaction of the ranges of velocity and depth. Recommended ranges for habitat variables associated with the highest densities of STJ Chinook Salmon include depths of 40–68 cm, velocities of 0.06–0.33 m/s, substrate sizes of 3–36 mm, and distances of 33–119 m to the main‐stem connection. Water temperatures associated with high juvenile densities varied by season (winter: 4–6°C; summer: 9–14°C).ConclusionOur recommended ranges for habitat variables can be used to refine designs for river restoration projects intended to improve habitat for juvenile Chinook Salmon and other salmonids in the Pacific Northwest.

中文翻译：

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影响华盛顿州斯卡吉特河流域洪泛区栖息地中溪流型幼年大鳞大麻哈鱼密度的变量

目标尽管进行了数十年的修复工作，奇努克鲑鱼斑鳟太平洋西北地区的野生动物仍然受到美国濒危物种法案（ESA）的保护。斯卡吉特河流域的奇努克鲑鱼对于普吉特湾奇努克鲑鱼进化重要单位的丰富和恢复发挥着至关重要的作用，该单位目前被欧洲航天局列为受威胁物种。斯卡吉特河中奇努克鲑鱼的溪流型幼鱼（STJ）生活史模式比帕尔或迁徙的鱼苗具有更高的成年期海洋存活率（即生产力），并且 STJ 奇努克鲑鱼栖息地的改善可以增加斯卡吉特河流域的丰富性和多样性。我们的目标是提供建议的变量范围，以影响 STJ 奇努克鲑鱼在洪泛区的栖息地选择。方法利用斯卡吉特河流域内 70 个地点的实地观测，我们开发了洪泛区栖息地三个季节的广义线性混合效应模型，以将变量关联起来。范围随 STJ 奇努克鲑鱼的密度而变化。结果模型精度随季节变化（夏季：右2= 0.24;冬天：右2= 0.56;春天：右2= 0.54），重要参数包括速度、基质、深度范围以及与主干最近连接的距离。其他重要因素包括木材覆盖、最高水温、速度范围以及速度和深度范围的相互作用。与 STJ 奇努克鲑鱼最高密度相关的栖息地变量的建议范围包括 40-68 cm 的深度、0.06-0.33 m/s 的速度、3-36 mm 的基质尺寸以及 33-119 m 到主干道的距离。茎连接。与高幼鱼密度相关的水温因季节而异（冬季：4–6°C；夏季：9–14°C）。结论我们推荐的栖息地变量范围可用于完善旨在改善幼鱼栖息地的河流恢复项目的设计西北太平洋地区的奇努克鲑鱼和其他鲑鱼。