The distribution and relative abundance of Westslope Cutthroat Trout (WCT) Oncorhynchus clarkii lewisi in relation to habitat characteristics remain unknown across large portions of the species’ range. The goals of this research were to provide a foundational understanding of WCT distribution and relative abundance related to habitat characteristics in tributaries of the St. Maries River, Idaho—a highly altered watershed. The basin drains an area of approximately 1,863 km² and has a longitudinal elevation difference of about 207 m. Backpack electrofishing and habitat assessments were conducted at 68 reaches in 35 different tributaries of the St. Maries River in 2017 and 2018. Habitat was measured at small (reach‐level) and large (watershed‐level) scales. A total of 652 WCT was sampled from 52 of 68 total reaches. Habitat characteristics varied by age‐class, but most WCT were estimated to be age 0 and age 1. Logistic regression models indicated that the presence of age‐0 WCT was positively related to stream gradient and elevation, but negatively related to water temperature, road density, fine substrate, stream depth, and the presence of Brook Trout (BKT) Salvelinus fontinalis. The relative abundance of age‐0 WCT was positively associated with road density and inversely related to wetted width, canopy cover, and elevation. The presence of age‐1 and older (age‐1+) WCT was positively related to gradient, canopy cover, and elevation, but negatively associated with road density, temperature, stream depth, and the presence of BKT. Relative abundance of age‐1+WCT was positively associated with gradient, large substrate, canopy cover, and road density. Conversely, the relative abundance of age‐1+WCT was inversely related to wetted width and elevation. This research indicates that WCT populations can persist in response to altered landscapes when suitable habitat exists. However, unmitigated threats, such as nonnative species competition (e.g., BKT), hybridization with Rainbow Trout O. mykiss, habitat loss, and habitat fragmentation, pose persistent complications to WCT abundance in locations where populations appear robust but their actual abundance is unknown.

中文翻译：

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在多个空间尺度上西坡残酷鳟鱼的分布和丰度与栖息地特征的关系

在该物种的大部分范围内，与栖息地特征相关的西坡斜th鳟（WCT）Oncorhynchus clarkii lewisi的分布和相对丰度仍然未知。这项研究的目的是提供对WCT分布以及与爱达荷州圣马里斯河支流（高度变化的分水岭）的栖息地特征相关的相对丰度的基础了解。流域排水面积约1,863 km ²且纵向高度差约为207 m。在2017年和2018年，在圣马里斯河的35个不同支流的68个河段进行了背包电捕鱼和栖息地评估。对生境的规模进行了小规模（到达水平）和大尺度（分水岭水平）的测量。从68个总河段中的52个取样了652个WCT。生境特征随年龄段而变化，但大多数WCT估计为0岁和1岁。逻辑回归模型表明，0岁WCT的存在与溪流坡度和海拔高度成正相关，而与水温，道路成负相关密度，细基质，水流深度以及溪鳟（Salvelinus fontinalis）的存在。0岁WCT的相对丰度与道路密度成正相关，而与湿宽度，冠层覆盖和高程成反比。年龄在1岁及以上（年龄在1岁以上）的WCT与坡度，树冠覆盖和海拔高度呈正相关，而与道路密度，温度，溪流深度和BKT呈负相关。1 + WCT的相对丰度与坡度，较大的基质，树冠覆盖和道路密度呈正相关。相反，年龄+ 1 + WCT的相对丰度与湿润的宽度和高度成反比。这项研究表明，当存在合适的栖息地时，WCT种群可以对景观变化做出反应。但是，未缓解的威胁，例如非本地物种竞争（例如BKT），与Rainbow Trout O. mykiss的杂交栖息地的丧失和栖息地的破碎化，在人口数量充沛但实际丰度未知的地方给WCT丰度带来持续的复杂性。