The role of estuaries in the ecology of adult Pacific salmon and trout in Puget Sound
The extensive loss or modification of estuaries throughout Puget Sound creates a significant challenge for adult salmon as they migrate to their natal streams to spawn. A 2024 report by University of Washington scientist Thomas Quinn looks at how different species of salmonids use estuaries to move from marine to freshwater environments. The report was commissioned by the University of Washington Puget Sound Institute with funding from the Environmental Protection Agency's National Estuary Program.
Each year, eight different species of salmon and trout migrate down rivers and into Puget Sound and other parts of the Salish Sea. They either migrate farther out to the Pacific Ocean or remain in the estuarine, nearshore, or open waters of the Salish Sea until they return and swim back upstream to spawn. Their use of estuary habitats as juveniles has been extensively studied, and restoration efforts have been completed or planned to improve habitat access and quality for juveniles. However, use of estuaries by adults has received much less attention, and that is the focus of this review. Estuary use by adults is important for salmon ecology and conservation because we have modified estuaries so extensively, and conduct commercial and recreational fishing in nearshore, estuary, and lower river habitats. The behavior of adults differs considerably among the species and populations, as they transition from salt to fresh water, from active feeding to anorexia, from immature to sexually mature fish, and from the orientation mechanisms that guided their migration in open water to those used during upriver migration. These complex factors and different behavior patterns cause salmonids to vary greatly in their duration in estuaries and exposure to fisheries, predators, and stressful environmental conditions.
