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The Fraser River Estuary: A global biodiversity hotspot

Where the Fraser River meets the sea, an extraordinary web of life converges. This estuary is irreplaceable.

Western Sandpiper walks along the shore, with a fact sheet looming in the foreground.
Photo by Alice Sun.
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The Fraser River Estuary is among the most productive and biologically diverse estuaries in North America.123. A crossroads for birds on three continents, it boasts the highest concentrations of migratory birds in Canada – with up to 1.4 million birds using it at peak season.45 Its ecological connections extend tens of thousands of kilometers across the Pacific Ocean through movements of migratory birds, mammals, salmon and other fish.6

600,000 Western Sandpipers

600,000 is the number of Western Sandpipers supported by Roberts Bank on a typical migration.7 Roughly half of the world’s population migrates through Roberts Bank each year.8

Recognized around the world

  • A global priority: international accreditations including a Global Key Biodiversity Area, Ramsar Convention on Wetlands, and the Western Hemisphere Shorebird Reserve’s highest recognition, emphasize its importance.9
  • Globally significant bird populations: The Estuary supports significant gatherings of birds, including Western Sandpipers, Dunlin, Brant and Trumpeter Swans.10

A refuge in every season

  • The Fraser River Estuary provides year-round feeding, and refuge for migrating birds, overwintering birds, returning adult salmon and rearing juvenile salmon.11121314
  • A diversity of feeding habitats: Dowitchers probe marshes for marine worms. Yellowlegs hunt small fish. Dunlins and Black-bellied Plovers search sandflats for worms.15
  • Habitat connectivity: The estuary contains Critical Habitat for the endangered Southern Resident killer whales16 and supports salmon returning to hundreds of natal streams and lakes in the Fraser River watershed.

Mudflats with crucial nutrients fuel migration

  • Microscopic algae support a food web: Biofilm, the thin layer of diatoms, bacteria and other tiny organisms, fuels migrating shorebirds on the Pacific flyway.1718
  • Energy-rich biofilm: Western Sandpipers use specialized tongues to slurp up the biofilm, rich with fatty acids, from the mud’s surface.19
  • A delicate balance of seasonal conditions produces the estuary’s biofilm..It peaks in the spring, coinciding with the migratory stopovers of hundreds of thousands of Western Sandpipers.20

Connected habitats for young salmon

  • Habitat en route to the sea and back: Marshes, eelgrass beds and sandflats in the estuary all support young salmon.21
  • Eelgrass supports fish diversity: 37 fish species have been found in eelgrass, compared with 19 in marshes and 22 on sandflats.22
  • A reconnected estuary: Raincoast’s newly built jetty breaches are restoring pathways between the Fraser River and the outer estuary, with monitoring confirming all species of young salmon use them.23

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Notes and references

  1. Short J. 2015. Expert submission to the National Energy Board on the fate and effect of oil spills from the Trans Mountain Expansion Project in Burrard Inlet and the Fraser River Estuary. JWS Consulting. Prepared for the Tsleil-Waututh Nation and partners. NEB Filing/Doc ID: A4L6A8 
  2. Butler R and Campbell W. 1987. The birds of the Fraser River delta: populations, ecology and international significance. Canadian Wildlife Service. Occasional Paper Number 65.
  3. Kehoe L, Lund J, Chalifour L, Yeganeh Asadian, Balke E, Boyd S, Carlson D, Casey J, Connors B, Cryer N, et al. 2020. Conservation in heavily urbanized biodiverse regions requires urgent management action and attention to governance. Conservation science and practice. 3(2). https://doi.org/10.1111/csp2.310.
  4. A Conservation Prospectus for the Fraser River Estuary. 2020. Prioritising conservation actions for ecological resilience ISBN: 978-1-9993892-3-9, Published by University of British Columbia, University of Victoria, MEOPAR and the Raincoast Conservation Foundation https://www.raincoast.org/reports/conservation-prospectus/ 
  5. Butler and Campbell, 1987.
  6. Short. 2015.
  7. Drever MC, Lemon MJF, Butler RW, Millikin RL. 2014. Monitoring populations of Western Sandpipers and Pacific Dunlins during northward migration on the Fraser River Delta, British Columbia, 1991-2013. Journal of Field Ornithology. 85(1):10–22. https://doi.org/10.1111/jofo.12045.
  8. Blondin AL, Drever MC, Flemming SA, Easton WE, Maftei M, Zharikov Y, Warnock N, Nol E. 2025. Lengths of Stay and Stopover Strategies of Western Sandpipers During Migration at Two Sites in British Columbia, Canada. Ecology and Evolution. 15(1). https://doi.org/10.1002/ece3.70739.
  9. Ramsar Convention Secretariat. 2012. Canada vastly extends Vancouver wetlands [Internet]; [accessed 2026 Sep 7]. https://www.ramsar.org/news/canada-vastly-extends-vancouver-wetlands
  10. Western Hemisphere Shorebird Reserve Network. n.d.-a. Fraser River Estuary [Internet]; [accessed 2026 Sep 7]. https://whsrn.org/whsrn_sites/fraser-river-estuary/
  11. Ramsar Convention Secretariat 2012.
  12. Western Hemisphere Shorebird Reserve Network n.d.-a.
  13. MacDuffee M. 2024. Coastal Connections: Southern Resident killer whales and Chinook salmon in Managed Extinction: the decline and loss of wild salmon and steelhead from the Pacific northwest. Ed Rick Williams and Jim Lichatowich. Caxton Press, Caldwell, Idaho
  14. Scott DC, Chalifour L, MacDuffee M, Baum JK, Beacham T, Rondeau E, Hinch SG. 2024 Aug 20. Variation in estuary use patterns of juvenile Chinook salmon in the Fraser River, BC. Canadian Journal of Fisheries and Aquatic Sciences. https://doi.org/10.1139/cjfas-2024-0012.
  15. Western Hemisphere Shorebird Reserve Network n.d.-a.
  16. Fisheries and Oceans Canada. 2018. Recovery strategy for the northern and southern resident killer whales (Orcinus orca) in Canada [Proposed]. Species at Risk Act Recovery Strategy Series. Ottawa (ON): Fisheries and Oceans Canada. x + 84 p. 
  17. Schnurr PJ, Drever MC, Elner RW, Harper J, Arts MT. 2020. Peak abundance of fatty acids from intertidal biofilm in relation to the breeding migration of shorebirds. Front Mar Sci. 7:63. https://doi.org/10.3389/fmars.2020.00063
  18. Western Hemisphere Shorebird Reserve Network n.d.-a.
  19. Schnurr et al. 2020.
  20. Chalifour L, Scott DC, MacDuffee M, Iacarella JC, Martin TG, Baum JK. 2019. Habitat use by juvenile salmon, other migratory fish, and resident fish species underscores the importance of estuarine habitat mosaics. Mar Ecol Prog Ser. 625:145-162. https://doi.org/10.3354/meps13064
  21. Chalifour et al. 2019.
  22. Chalifour et al. 2019.
  23. Raincoast Conservation Foundation. n.d. Protecting salmon habitat: removing barriers in the fragmented Fraser River Estuary [Internet]; [accessed 2026 Sep 9]. https://www.raincoast.org/habitat/

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