Migration and repeat spawning dynamics of acoustically tagged Atlantic salmon (Salmo salar) kelts through the Gulf of St. Lawrence

Atlantic salmon (Salmo salar) display diverse life history strategies, with some spawning more than once. Repeat spawners are often overlooked in population assessments. We analyzed acoustic telemetry data from 530 post-spawned salmon (kelts) tagged in three Canadian rivers (Miramichi, Restigouche, Cascapedia) over 11 years (2008–2019) to examine (1) the frequency of repeat spawning across populations and time, (2) the relative importance of consecutive versus alternate reconditioning strategies, and (3) spatial and temporal migration dynamics through the Gulf of St. Lawrence (GoSL). Overall, 15.5% of tagged kelts were detected returning to rivers to spawn in consecutive (8.4%) or alternate years (6.8%). Alternate spawners from all three rivers entered the labrador sea through the Straight of Belle Isle synchronously, suggesting an environmental influence. Our findings reveal population-specific variation and condition-dependent plasticity in reconditioning behaviour, highlighting the importance of accounting for repeat spawners in assessments and management of Atlantic salmon populations to promote their resilience.