Variation in seasonal survival rates, densities and growth rates of coastal cutthroat trout (Oncorhynchus clarkii clarkii) were assessed across a size gradient of small, forested streams in the Pacific Northwest. We used a robust, mark-recapture study, stratified seasonally to estimate monthly survival rates of trout in coastal British Columbia (not including young-of-the-year). Survival estimates showed that the summer season had the lowest monthly survival rates (0.907) across all streams in our study (0.927 remainder of year). Within the size range of the seven small streams studied, low-flow habitat availability (defined by residual pool depth in summer) was the best predictor of mean monthly survival rates, supporting the hypothesis that trout survival increases with the quantity of aquatic habitat, particularly depths of residual pools. In addition, there was an asymptotic relation between water depth and survival rates, where beyond ~20 cm of residual pool depth, greater depth did not confer greater rates of trout survival. Growth rates in all but the largest stream were also lowest during summer. While densities tended to be higher in streams with greater residual depth, this was not significant. Body mass in a given season was a good predictor of survival to the next sampling period. The distribution and success of resident cutthroat trout populations in small streams appear to be constrained by summer low-flow periods and specific geomorphologies that support deeper pools.

中文翻译：

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不列颠哥伦比亚省西南部不同河流大小的沿海凶残鳟鱼的季节特定存活率和密度

沿海割喉鳟 ( Oncorhynchus clarkii clarkii ) 季节性存活率、密度和生长速率的变化) 在太平洋西北部的小型森林溪流的大小梯度上进行了评估。我们使用了一项稳健的标记重新捕获研究，按季节分层来估计不列颠哥伦比亚省沿海鳟鱼的月存活率（不包括当年幼鱼）。生存估计显示，在我们研究的所有溪流中，夏季的月生存率最低（0.907）（一年的剩余时间为 0.927）。在所研究的七条小溪流的大小范围内，低流量栖息地可用性（由夏季的剩余水池深度定义）是平均月存活率的最佳预测指标，支持了鳟鱼存活率随着水生栖息地数量增加而增加的假设，特别是残池深度。此外，水深与存活率之间存在渐近关系，在超过约 20 厘米的剩余池深度的地方，更深的深度并没有带来更高的鳟鱼存活率。除了最大的溪流之外，其他所有溪流的增长率在夏季也是最低的。虽然残留深度较大的溪流中的密度往往较高，但这并不显着。特定季节的体重可以很好地预测下一个采样期的存活率。小溪流中常驻割喉鳟种群的分布和成功似乎受到夏季低流量期和支持更深水池的特定地貌的限制。特定季节的体重可以很好地预测下一个采样期的存活率。小溪流中常驻割喉鳟种群的分布和成功似乎受到夏季低流量期和支持更深水池的特定地貌的限制。特定季节的体重可以很好地预测下一个采样期的存活率。小溪流中常驻割喉鳟种群的分布和成功似乎受到夏季低流量期和支持更深水池的特定地貌的限制。