New research by NOAA Fisheries and partners reveals unexpected behaviors in juvenile salmon migration, challenging long-held beliefs about their life cycle.
For decades, scientists believed that juvenile salmon followed a linear migration route: hatching in freshwater, heading to the ocean to mature, and returning to their birthplace to spawn. But new findings published in Frontiers in Ecology and the Environment challenge this narrative. The study reveals that young salmonids—including coho salmon, steelhead, and cutthroat trout—often migrate in a far more dynamic and complex way.
Juvenile Salmon Use Coastal “Meta-Nurseries”
Researchers observed that up to 22% of tagged juvenile salmon in Washington and California moved back and forth between saltwater and freshwater systems—sometimes up to nine times. These fish traveled along the Pacific coastline, exploring rivers as far as 40 miles away from their original stream.
These interconnected coastal zones act as “meta-nurseries”, offering rich, diverse habitats for juvenile fish. The migration paths included Deep Creek, East Twin River, and West Twin River on Washington’s Olympic Peninsula, with some fish staying in non-natal rivers for up to 305 days.
Why Juvenile Salmon Are Roaming
This exploratory behavior helps salmonids find better feeding grounds, avoid predators, and escape unstable stream conditions caused by heavy rain and flooding. According to lead author Dr. Stuart Munsch of NOAA’s Northwest Fisheries Science Center, “The landscapes are much more connected than we realized, and salmon take advantage of that.”
By spreading out their movements, young salmon reduce competition, locate new habitats, and potentially increase their survival chances amid climate and environmental changes.
Fish Tagging Reveals Hidden Movements
Scientists used microchip tagging technology to track nearly 900 juvenile salmonids across different watersheds. They noticed a range of behaviors—from brief visits to neighboring rivers to overwintering in entirely different drainages. In Northern California, one coho salmon swam from a Redwood Creek tributary all the way to Humboldt Bay—a journey of 40 miles.
These findings may only scratch the surface, as many drainages are not yet equipped with monitoring devices. Therefore, the actual number of fish making these cross-drainage migrations may be significantly higher.
Benefits and Risks of River-to-River Migration
While this behavior allows juvenile salmon to find optimal conditions for growth, it also comes with risks. Traveling through saltwater multiple times exposes them to more predators. Yet the trade-off may be worth it: greater resilience and adaptability in changing environments.
“By moving around, they are spreading the risk,” Munsch explained. “Some may find alternative habitats that better support them as conditions change.”
Rethinking Salmon Conservation
These findings challenge the traditional textbook model of salmon migration. Co-author Todd Bennett of NOAA emphasized the need for adaptive management strategies: “We wouldn’t know about this unless we happened to be looking. Even after decades of research, salmon still surprise us.”
Understanding the full range of juvenile salmon movements is crucial for shaping future conservation efforts and protecting these iconic fish in a rapidly changing world.
Key Takeaways:
- Juvenile salmon can travel between saltwater and multiple freshwater rivers before adulthood.
- Up to 22% of tracked fish exhibited this behavior, sometimes moving 9 times between watersheds.
- These movements improve survival by helping fish locate safer, richer habitats.
- Researchers urge a shift in salmon management strategies based on these findings.
Source:
Munsch, S.H., Bennett, T.R., et al. Juvenile salmonids traverse coastal meta-nurseries that connect rivers via the sea. Frontiers in Ecology and the Environment (2025). DOI: 10.1002/fee.2848