By Ned Rozell
In early November, a time when shadows lengthen and deep cold hardens the landscape, chum salmon have returned to spawn in the lower Delta River. In spots, the water is so shallow that dorsal fins wiggle in the frigid air. Some fish get frostbite on really cold days.
Now is the peak of one of Alaska’s last great animal migrations of the year. Thousands of “fall run” chum salmon are hanging a right from the Tanana River into a few crystal channels of the Delta River.
These fish are at the end of their four-year lives. The tiger-striped dog salmon began a 1,100-mile journey from the Bering Sea from mid July through early September.
The Yukon River run of chum salmon is the largest in the world. Most years, three times as many fish than there are people in Alaska migrate up the Yukon. This year is an exceptional run, with 5 million chums jetting up the river, including 2.3 million fall chums returning to the Delta River and elsewhere.
These arm-length fish, larger than summer-run chums that returned in the warmth of solstice, are stacked at a deep aqua crescent where the Delta shoves into the Tanana River, right next to the Richardson Highway bridge.
Out of the pile, chums blast forward into the clean water of the Delta, just inches deep in spots. Males have wolfish jaws with overlong snouts. Females full of eggs sport the same pink and black stripes on torpedo bodies. None of the fish have eaten in more than a month, since they left salt water to nose back to their birth stream.
Unlike in summer, the Delta’s water is now transparent. Until mid-October, it flowed deep and cloudy with glacial dust it carried in the meltwater from Alaska Range glaciers.
In this lowest one mile of the river, close to the highway and nearby trans-Alaska pipeline, upwelling springwater keeps the river from freezing to the bottom. That is perhaps what first attracted the salmon to this spot, probably thousands of years ago: water that remains 4 degrees above freezing, allowing eggs to survive one foot beneath surface air that is 40 below.
Within these few watery acres of nesting habitat, female chums brush the river gravel with their tails, creating a depression called a redd. Into that, they spill more than 3,000 eggs. At the same time, male salmon deposit their milt. The female then fans her tail over the spot again, covering the fertilized eggs with gravel.