Inshore marine coastal zone migration patterns in Atlantic salmon post-smolts emigrating from eight rivers in north-east Scotland.

Atlantic salmon, Salmo salar, migrate through multiple habitat types, each having the potential to impact differently upon migration success. The inshore marine coastal zone is arguably disproportionately impacted by potential stressors on populations. We investigated the migration of Atlantic salmon post-smolts (n = 898) from eight rivers (populations) through the inshore marine coastal zone over a 2-year period using acoustic telemetry. Migration success through marine inlets where fish first entered seawater, and through the wider inshore marine coastal area (the Moray Firth, north-east Scotland) was consistently high across populations and across years (mean = 77%). There was no evidence of the high inshore marine predation rates reported elsewhere. Post-smolts utilised well-defined inshore marine migration pathways that were broadly consistent among populations and over time. The pace of migration through the inshore marine coastal habitat was also consistently rapid across populations and time, with the period of migration being seasonally constrained (mean across population = 36.5; range 18-45 days). Taken together with existing literature, this study suggests that the patterns of migration of Atlantic salmon post-smolts through the inshore marine coastal zone are likely highly environment specific.