Density-dependent (DD) and density-independent (DI) effects play an important role in shaping fish growth rates, an attribute that correlates with many life history traits in fishes. Consequently, understanding the extent to which DD and DI effects influence growth rates is valuable for fisheries assessments because it can inform managers about how populations may respond as environmental conditions continue to change (e.g., threats from climate change). We used a Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis (RGCT) capture–mark–recapture data set collected over 2 years along a temperature and density gradient in northern New Mexico streams to test the extent to which DD and DI effects interact to influence specific growth rates. We found that temperature (DI) and density (DD) interacted with RGCT life stage (i.e., immature or mature) to affect growth rates. We only detected evidence of a negative DD effect on RGCT growth for the immature fraction of a population when exposed to the warmest stream temperatures. Our results suggest that competition most strongly affected the immature portion of RGCT populations, and this effect was only detectable when temperatures were warmest and energetic stress was likely at its highest. The quadratic relationship between temperature and growth rates also demonstrated that stream temperatures were below as well as above optimal growth temperatures for RGCT. Growth rates in our RGCT populations were influenced by complex interactions of DD and DI effects, and our results suggest that the negative consequences of warming trends associated with climate change on RGCT populations may be exacerbated by DD effects.

中文翻译：

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密度相关和密度无关因素对西南割喉鳟鱼种群增长率的交互作用

密度相关 (DD) 和密度无关 (DI) 效应在塑造鱼类生长率方面发挥着重要作用，这一属性与鱼类的许多生活史特征相关。因此，了解 DD 和 DI 影响对增长率的影响程度对于渔业评估很有价值，因为它可以告知管理人员随着环境条件的持续变化（例如，气候变化的威胁）种群可能如何应对。我们使用了 Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis(RGCT) 捕获-标记-重新捕获数据集沿新墨西哥州北部河流的温度和密度梯度收集了超过 2 年，以测试 DD 和 DI 效应相互作用以影响特定增长率的程度。我们发现温度 (DI) 和密度 (DD) 与 RGCT 生命阶段（即未成熟或成熟）相互作用以影响生长速率。我们仅检测到当暴露于最温暖的溪流温度时，对种群未成熟部分的 RGCT 生长产生负面 DD 影响的证据。我们的结果表明，竞争对 RGCT 种群的未成熟部分的影响最强烈，这种影响只有在温度最高且能量压力可能最高时才能检测到。温度和生长速率之间的二次关系也表明流温度低于和高于 RGCT 的最佳生长温度。我们的 RGCT 种群的增长率受到 DD 和 DI 效应复杂相互作用的影响，我们的结果表明，与气候变化相关的变暖趋势对 RGCT 种群的负面影响可能会因 DD 效应而加剧。