Chinook return to the Sammamish through one of its warmest, slowest reaches

Chinook salmon are back in the lower Sammamish River.¹ Over the past four weeks they have been seen along the slow, dredged reach that runs from Kenmore through Bothell toward Woodinville, with a scattering of other sightings toward Edmonds and across the Sound on the Kitsap side.¹ These are adults on the last leg of a trip that began in the North Pacific and passed through the Ballard Locks sometime this summer.

The Chinook (Oncorhynchus tshawytscha) is the largest of the Pacific salmon and the easiest to name with the fish in hand: black gums along the lower jaw where a coho's are white, and small dark spots across both lobes of the tail rather than just the upper one. In salt water they are silver with a blue-green back. By the time they reach a river like this one they are darkening to bronze and olive, the males growing the hooked snout and heavy teeth they will use to fight for position on the gravel. Lake Washington fish typically run ten to twenty-five pounds, three to five years old.

What they are doing right now is mostly waiting. Adults enter Lake Washington through the locks from June into September and hold in the lake's cooler depths, then push up the Sammamish toward Bear Creek, Cottage Lake Creek and Issaquah Creek to spawn from mid-September into November. The Sammamish is the bottleneck. It was straightened and dredged in the 1960s, runs shallow and slow through open valley floor, and is one of the warmest salmon rivers in the region in late summer. Fish moving through it in August and early September are traveling in water that regularly sits near the twenty-degree mark where migrating salmon start to burn energy they cannot spare.² Cooler nights and the first fall rains are what open the door upstream.

Snohomish County's dry spell, described here two weeks ago, has not let up; a little over half the county has sat in moderate drought since the third week of August, and the past month at Paine Field ran about 2.7 degrees above normal for daily highs.^3, 4 Those numbers describe the air and the land, not the river, and no current gauge reading on the Sammamish was available to say how the water itself is running.⁵ The fish are in it regardless.

Once they spawn, Chinook do the thing no other family of fish does at this scale: they die on the gravel and stay. A single carcass feeds bears, otters, eagles, gulls, dippers and the insects the next generation of fry will eat; the nitrogen from an ocean life ends up in streamside alders and cedars. The eggs overwinter in the gravel, the fry emerge in late winter, and most of this run's young will spend only a few months in fresh water before dropping down through the lake and out the locks, small enough to fit in a palm.

Puget Sound Chinook have been listed as threatened under the Endangered Species Act since 1999, and the Lake Washington run is among the more heavily worked-on in the region.^6, 7 Adopt A Stream Foundation does its stream restoration from North Creek in Everett, a tributary that meets the Sammamish at Bothell, right in the stretch where these fish were seen.

Anyone who wants to watch the run can do it without waders. The fish ladder windows at the Ballard Locks show Chinook passing into the lake through September, and by early October they will be on the gravel in Bear Creek and Issaquah Creek, where a footbridge is all the equipment needed.