Lower Columbia River chum salmon finished spawning in late December, and biologists say the returns look good for the threatened species this year.
Biologists counted well over 500 chum salmon nests -- redds -- in the mainstem below Bonneville Dam.
The 2010 chum return is good, but not record-breaking, says BPA fisheries biologist Scott Bettin.
“Chum are a different fish,” says Bettin, “and we don’t really know as much about what affects them.”
Chum, listed under the Endangered Species Act, don’t spend much time in the river -- they hatch and leave for the ocean right away. They spawn below the dams, so they’re not affected by dam passage. They are harvested almost solely in the ocean.
Operators manage the water elevations and flow levels below Bonneville Dam from early November through early April to help the chum spawn safely. This year, they began additional water releases from Bonneville Dam on Nov. 1 to encourage the females to place their redds at an elevation that could be maintained through early April. The first redds were spotted at Ives Island Nov. 2.
In late December, when no more new redds were showing up in spawning surveys, federal agencies consulted with tribes and states to decide on the elevation and flow levels that would best keep the redds covered while also refilling reservoirs to boost flows for other migrating salmon in the spring.
The level is a little higher than usual, says Bettin, because the heavy rains in November and December meant river levels were higher when the chum established their redds. Operators will continue to monitor redd temperatures and manage flows below Bonneville to keep the redds covered until early April when the chum fry will finish emerging.
The first ones to hatch and head out to the ocean could leave as early as January, says Bettin. “They’re the last in, first out,” he says. In order to incubate that quickly, the chum have to plant their eggs in ground water upwelling or near hot springs in shallow water. Like other salmon, they stay in the ocean for two to five years before they return to the river to spawn.