It’s not often that you get to witness the beginning of an ecological revolution. Estuaries, places where fresh and salt water mix, are being restored at locations across Puget Sound. Scientists hope this will create much needed habitat for endangered Chinook salmon that rely on estuaries as they grow and prepare for their lives in the open ocean. Recently, we visited zis a ba, an estuary recovery project led by the Stillaguamish Tribe near the mouth of the Stillaguamish River.
More than 90 percent of Puget Sound’s tidal wetlands have been lost to development. These rare estuaries, where tidal flows mix with outputs from local rivers, are critical to the early life stages of Chinook and other salmon. A restoration project near Port Susan Bay at the mouth of the Stillaguamish River is bringing back some of this vital habitat.
Chinook salmon, the largest adult Pacific salmon, rely heavily on estuaries for their survival. Juvenile Chinook enter estuaries at a range of different times and sizes depending on their ‘type’. Ocean-type Chinook tend to migrate to estuaries immediately, while stream-types spend up to a year in rivers before migrating. Both types use estuaries to feed and grow while adjusting to saltier waters. The juveniles spend upwards of 33 days in estuaries, making these tidal marshes crucial to their livelihoods. The Stillaguamish Tribe’s zis a ba project will restore estuarine habitat for juvenile Chinook and other salmon to use. Chinook salmon populations using the Stillaguamish River and its estuaries are listed as Threatened under the Endangered Species Act.
Although a future home for salmon, zis a ba II currently consists of agricultural and industrial land recently purchased by the Stillaguamish Tribe. The site, which will be transformative for regional Chinook populations, has had a range of historical uses. Once used by a transportation company, tire piles and abandoned tractor-trailers will be removed from the property. Currently, the area is being leased by the Stillaguamish Tribe to local farmers to grow crops such as alfalfa, grass for seed, and corn. After dikes are carefully breached to allow the tide to again flow over the land, ecologists hope that a new type of “crop” (tidal marsh land) will support salmon and other native species.
When Europeans first occupied the land around the Stillaguamish River Delta, they diked the river to stop the tides from overflowing into nearby marshland. The resulting levee allowed the surrounding area to dry out and be used for farming. The Stillaguamish Tribe will push back two miles of the levee currently surrounding Hat Slough along the Stillaguamish River to restore tidal marsh habitat for juvenile Chinook.
Distributary channels, which flow away from the main stem of a river, are important highways for young salmon seeking tidal marshes as they move from freshwater to saltwater. Distributary channels started by The Nature Conservancy on land adjacent to the zis a ba II restoration site will eventually be extended by the Stillaguamish Tribe to connect them to nearby Hat Slough on the Stillaguamish River.
The red paths and arrows drawn on this aerieal image show the longer route that outmigrating juvenile salmon must currently follow, all the way around to access the estuarine marsh they need to feed and grow while they adjust to saltwater.
Annotated Google Earth map provided by Charlotte Scofield, Stillaguamish Tribe.
The white lines here indicate where distributary channels will be created across zis a ba II as a shortcut (red lines) for juvenile salmon to more easily access the tidal marsh they need before migrating to sea at the nearshore of Port Susan Bay.
Annotated Google Earth map provided by Charlotte Scofield, Stillaguamish Tribe.
In 2018, the Stillaguamish Tribe completed zis a ba I, an 87-acre tidal marsh restoration project, which set the stage for the tribe’s future projects: zis a ba II and zis a ba III. Zis a ba II is estimated to be completed by 2026, followed by zis a ba III. Once completed, the three projects will restore more than 800 acres of lost tidal marsh habitat crucial to the threatened Chinook salmon species.
Watch for more stories about zis a ba and the new science driving estuary recovery in our magazine Salish Sea Currents.
About the authors:
Mary Flynn is an undergraduate student double majoring in marine biology and environmental science and terrestrial resource management. She is a 2024 PSI summer intern supported by the University of Washington EarthLab program. Sylvia Kantor is Assistant Editor at the Puget Sound Institute.