Individual variation in movement throughout the life cycle of a stream-dwelling salmonid fish

Stream-dwelling fish populations have long served as important models of animal movement. Populations of adult stream-dwelling fishes are generally composed of a mix of relatively sedentary and mobile individuals. However, we do not know whether this pattern that we typically observe among adults is indicative of patterns of movement that occur throughout the life cycle. Therefore, we do not know whether we can apply these patterns to understanding or predicting processes such as migration and thus the potential for the evolution of genetic differences among populations. We test the general hypothesis that patterns of movement throughout the life cycle are consistent with patterns of movement inferred by indirect genetic methods and, more specifically, that the characteristics of the mobile fraction of the population are consistent with patterns of genetic differentiation. We used parentage analyses to infer the movements of alevin brook charr (Salvelinus fontinalis) in Freshwater River, Newfoundland, Canada, and a capture-recapture study of one cohort in this population to infer movement throughout the rest of the life cycle. We found that alevins move large distances shortly after emergence, primarily in the downstream direction, and that the population is composed of a mix of relatively sedentary and mobile individuals throughout all other intervals of the life cycle. In contrast, when we considered movements of individuals first captured as juveniles and eventually recovered as reproductively mature adults, we found relatively large and uniform distributions of net movement distance. Thus, heterogeneity in individual movement of adults is not representative of patterns of movement throughout the life cycle and therefore may provide only limited inference of population-level processes such as gene flow.