Abstract: Population persistence across broad spatial scales (e.g., watersheds) can depend on asynchronous dynamics among populations at finer scales (e.g., streams or habitats). We applied a von Bertalanffy growth model and closed N‐mixture abundance model in a hierarchical Bayesian framework to examine effects of fine‐scale variability in temperature and density dependence on growth and abundance as well as within‐ versus among‐stream variability in growth and abundance of Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis (RGCT) in northern New Mexico streams. An accumulation of degree‐days positively influenced instantaneous growth rates and, to a lesser extent, negatively affected asymptotic body length. A nonlinear response [...]