Genetic Population Structure of Brook Trout Inhabiting a Large River Watershed

Abstract

Abstract The genetic population structure of brook trout Salvelinus fontinalis inhabiting the Miramichi River, New Brunswick, a large (14,000-km2) river system composed of three main stems, was assessed using six microsatellite DNA loci. Samples from 12 sites incorporating four temporal replicates were analyzed. An individual-based assignment method without a priori knowledge of geographic origin suggested the presence of five candidate source populations within the 12 sites. Drainage structuring based on the 12 sampling sites did not explain the observed patterns of genetic population structure (analysis of molecular variance: 0.74% of variance explained; not significant). Conversely, the five candidate source populations estimated under the assignment approach significantly explained the genetic population structure observed (3.47% of variance explained; P < 0.001), the level of population fragmentation within sampling sites increasing significantly with proximity to the mouth of the watershed (P = 0.01...