Cindy Breau

1 INTRODUCTION Populations of Atlantic salmon (Salmo salar) have been declining in abundance over the past few decades and are targeted by conservation efforts throughout its range (Aas et al., 2010; Gillis et al., 2023; Smialek et al., 2021).

1 INTRODUCTION Transition zone habitats are important structural elements of ecosystems that mark a gradual or abrupt change from one ecological unit (e.g., habitat or community) to another (Kark, 2012; P. A. Delcourt & H. R. Delcourt, 1992).

1 INTRODUCTION Spatial synchrony is a common pattern of change through time among geographically distinct populations or species. Spatial synchrony can arise as the result of gene flow, trophic interactions, and/or shared environmental conditions (Bjørnstad et al., 1999; Moran, 1953; Walter et al., 2017).