Dispersal and gene flow in anadromous salmonids: a systematic review

Abstract

Dispersal is a ubiquitous ecological process that has been extensively studied in most groups of organisms. Despite several evidence and earlier reviews, dispersal and its implications are still overlooked in salmonids, where homing is the predominant strategy. We provide a systematic and updated review of dispersal and gene flow among several species of anadromous salmonids. The 372 reviewed studies were unevenly distributed among species, with Atlantic salmon and sea trout being the most studied. A significant proportion of studies focused on the genetic differentiation between populations without estimating dispersal, while others examined straying from hatchery fish. Few studies investigated dispersal on wild populations and a few modelling approaches were developped on the topic. We highlight various facets of dispersal, including the terminology, metrics, methods, and spatio-temporal scales used. We showcase a strong variability in estimated rates within and between studies, which is likely related to methodologies, species propensity, and spatial systems. We also investigated the relationship between dispersal metrics and distance. Finally, we emphasize a lack of knowledge on the drivers of dispersal and that still few studies consider, and even fewer assess, the implications of dispersal for the conservation and management of salmonids.