Zabel Richard W
National Marine Fisheries Service, Seattle, Washington 98112, USA.
Am Nat. 2002 Apr;159(4):372-87. doi: 10.1086/338993.
For migratory species, duration of migration, or "travel time," is often a critical variable in determining the cost of migration. Observed travel times are the result of both environmental factors such as air or water currents and the behavior of individuals. In an effort to distinguish among these components, I developed a migration model based on an advection-diffusion equation that characterizes population movements in terms of two biologically meaningful parameters: migration rate and rate of population spread. I applied the model to travel time data from juvenile chinook salmon (Onchorhynchus tshawytscha), which were tagged during their seaward migration. The tagged fish originated from three separate evolutionarily significant units (ESUs) as classified by the U. S. National Marine Fisheries Service. The model was expanded by allowing migration and diffusion rates to vary with fish length and river flow. Variability in travel times explained by these factors was strikingly similar from year to year within ESUs, and the migratory behavior revealed by the analysis was consistent with the life-history patterns that distinguish the ESUs. The approach presented here is easily adaptable to a wide range of migratory species and may be particularly useful for predicting how at-risk populations respond to variable conditions in regulated or otherwise disturbed migration habitats.
对于洄游物种而言，洄游持续时间，即“旅行时间”，通常是决定洄游成本的关键变量。观测到的旅行时间是诸如气流或水流等环境因素以及个体行为共同作用的结果。为了区分这些组成部分，我基于平流扩散方程开发了一个洄游模型，该模型用两个具有生物学意义的参数来描述种群运动：洄游速率和种群扩散速率。我将该模型应用于幼年奇努克鲑（Onchorhynchus tshawytscha）的旅行时间数据，这些鱼在向海洄游期间被标记。这些被标记的鱼来自美国国家海洋渔业局分类的三个不同的具有进化意义的单元（ESUs）。通过允许洄游和扩散速率随鱼的长度和河流流量变化，对模型进行了扩展。在各ESU内，由这些因素解释的旅行时间变化年复一年惊人地相似，分析揭示的洄游行为与区分各ESU的生活史模式一致。这里介绍的方法很容易适用于广泛的洄游物种，对于预测濒危种群如何应对受管制或其他受干扰的洄游栖息地中的可变条件可能特别有用。
