Changes in adult Atlantic salmon (Salmo salar) run timing in the Miramichi River, New Brunswick, in relation to river temperature and discharge rates over seven decades

Abstract

Atlantic salmon (<i>Salmo salar</i>) is a culturally, economically, and ecologically important species in Eastern Canada. Populations have been declining in recent decades, which can have negative implications for livelihood, ecosystems, and local tradition. Ecological factors associated with climate change in aquatic systems including temperature and river flow can alter the upstream migration behaviour of adult salmon. River entry during upstream migration for spawning, or “run timing”, is a critical life history event for this species. This project found that run timing has significantly changed in the Miramichi River between 1952-2021. To investigate whether this change is associated with ecological factors in freshwater, I examined the relationship between freshwater environmental predictor variables – temperature and discharge rate – and Atlantic salmon entry to the estuary. Unlike previous work on smaller freshwater tributaries, there were no strong relationships found between entry to the estuary from the ocean and freshwater variables.