Huntsman Brock M, Falke Jeffrey A, Savereide James W, Bennett Katrina E
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America.
U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America.
PLoS One. 2017 May 22;12(5):e0177467. doi: 10.1371/journal.pone.0177467. eCollection 2017.
Density-dependent (DD) and density-independent (DI) habitat selection is strongly linked to a species' evolutionary history. Determining the relative importance of each is necessary because declining populations are not always the result of altered DI mechanisms but can often be the result of DD via a reduced carrying capacity. We developed spatially and temporally explicit models throughout the Chena River, Alaska to predict important DI mechanisms that influence Chinook salmon spawning success. We used resource-selection functions to predict suitable spawning habitat based on geomorphic characteristics, a semi-distributed water-and-energy balance hydrologic model to generate stream flow metrics, and modeled stream temperature as a function of climatic variables. Spawner counts were predicted throughout the core and periphery spawning sections of the Chena River from escapement estimates (DD) and DI variables. Additionally, we used isodar analysis to identify whether spawners actively defend spawning habitat or follow an ideal free distribution along the riverscape. Aerial counts were best explained by escapement and reference to the core or periphery, while no models with DI variables were supported in the candidate set. Furthermore, isodar plots indicated habitat selection was best explained by ideal free distributions, although there was strong evidence for active defense of core spawning habitat. Our results are surprising, given salmon commonly defend spawning resources, and are likely due to competition occurring at finer spatial scales than addressed in this study.
密度依赖（DD）和密度独立（DI）的栖息地选择与物种的进化历史密切相关。确定每种选择的相对重要性是必要的，因为种群数量下降并不总是DI机制改变的结果，而往往可能是由于DD导致的承载能力下降。我们在阿拉斯加的切纳河建立了时空明确的模型，以预测影响奇努克鲑鱼产卵成功率的重要DI机制。我们使用资源选择函数，根据地貌特征预测适宜的产卵栖息地，使用半分布式水能量平衡水文模型生成水流指标，并将溪流温度建模为气候变量的函数。根据洄游估计（DD）和DI变量，预测了切纳河核心和周边产卵区的产卵者数量。此外，我们使用等值线分析来确定产卵者是积极捍卫产卵栖息地还是沿河流景观遵循理想自由分布。空中计数最好由洄游数量以及对核心区或周边区的参考来解释，而候选集中没有支持包含DI变量的模型。此外，等值线图表明栖息地选择最好由理想自由分布来解释，尽管有强有力的证据表明核心产卵栖息地存在积极防御。鉴于鲑鱼通常会捍卫产卵资源，我们的结果令人惊讶，这可能是由于竞争发生在比本研究中所涉及的更精细的空间尺度上。
