Abstract
Quantifying the scale of offspring dispersal is essential for understanding demographic connectivity across landscapes and rates of population spread. However, characterizing natal dispersal in fishes is complicated by the difficulties of tracking origins and movement during early life-history stages. We combined direct observation of natal dispersal based on otolith chemistry with indirect estimates of dispersal from population genetics to quantify intergenerational dispersal of smallmouth bass (Micropterus dolomieu) inhabiting a river network. Average parent–offspring dispersal was estimated as 7.7 km from genetic isolation-by-distance and demographic population data. Otolith chemistry indicated that adults were captured an average of 8.3 km from their natal tributary, supporting the genetics-based estimate. Our estimate of intergenerational dispersal is higher than previous estimates for lotic fishes and considerably higher than estimates for smallmouth bass in lake systems. Differences in availability of seasonal habitats for smallmouth bass may account for the contrasting scales of dispersal between lake and river populations. The large intergenerational dispersal distance of riverine smallmouth bass should be considered in conservation of fisheries or efforts to control invasive populations in river networks.
Highlights
Understanding the scale of intergenerational dispersal in populations provides important information for species management and conservation planning
While natal dispersal is the movement of an individual from its birth site to its breeding site (Stenseth and Lidicker 1992), intergenerational dispersal is the spatial extent of natal dispersal of all offspring of a breeding pair
Genetic analysis demonstrated spatial structure among smallmouth bass populations of the James River basin influenced by tributary–mainstem differentiation and a pattern of isolation-by-distance
Summary
Understanding the scale of intergenerational dispersal in populations provides important information for species management and conservation planning. Measuring intergenerational dispersal is difficult for most wild populations This is true for fish populations due to the challenges of tracing movement through early life history, when locating or marking individuals may be impossible. Natural tags, such as chemical signatures recorded in fish “hard parts” like otoliths, can provide inference on natal origins under appropriate conditions of spatial heterogeneity, temporal persistence, and reliable incorporation of site-specific chemistry (Elsdon et al 2008; Pracheil et al 2014; Carlson et al 2017). Spatial variation in elemental isotopic ratios such as 87Sr/86Sr often provide
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