"It's sort of a wait-and-see situation right now," said Craig Bartlett, a spokesman for the Washington Department of Fish and Wildlife.
The landslide killed the eggs in the nests buried deep underneath its mud, but it will take years before the impact on the Chinook and steelhead runs can be determined. That's because this year's fry, which typically spawns both up and downstream of the mudslide, has yet to return to the river, according to Bartlett.
Steelhead typically swim upstream on the Stillaguamish between March and May; Chinook, between June and August. This year, many will be blocked from their typical spawning habitat. It remains to be seen whether or not they'll adapt, spawning downstream instead where Bartlett says a narrow channel has been carved out.
In Puget Sound, newborn Chinook and steelhead — before the habits of nature and humans take their toll — collectively number only in the tens of thousands. The Stillaguamish runs, each of which counts roughly 800 returning fish each spring and summer , are a subset of those species.
Still, he is optimistic. "This is hardly the first time this has happened to the river," he said. "This river is highly prone to mudslides."
The Stillaguamish runs are small when compared to the nearby Skagit River, which is also a spawning area for Chinook and steelhead.
"But 'it's not a shrug of the shoulder,' because the Puget Sound steelhead and Chinook are listed as threatened," Bartlett said.