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Channel Rehabilitation Below Bonneville Dam Brings Big Boost To ESA-Listed Chum Salmon Spawners
Posted on Friday, December 02, 2011 (PST)

The newly restored and expanded Hamilton springs channel just off the Columbia River below Bonneville Dam has become the destination of choice this year for a much greater than average number of threatened chum salmon spawners.

 

“Live counts” elsewhere up and down the lower Columbia River have been promising, but the off-channel area a little more than a mile up Hamilton Creek has been inundated with fish.

 

A Nov. 23 survey produced a count of 506 live fish milling around in the channel. That compares to a recent average annual high count of 171 over the past seven years, according to the Washington Department of Fish and Wildlife’s Todd Hillson.

 

The live count was down to 372 adult chum Monday, but the most recent surveys show 50-75 adults spawning in the creek. So the majority are using Hamilton Springs channel, which is a good thing, Hillson said.

 

“It’s definitely an uptick,” he said of the fish numbers. Numbers elsewhere also appear relatively strong. Counts are up over last year in southwest Washington’s Grays River, a relative stronghold for a Columbia River chum stock that was listed under the Endangered Species Act in 1999. The Grays River feeds into the Columbia in the lower estuary; Hamilton’s confluence with the big river is just below Bonneville Dam.

 

Mainstem Columbia River spawners in areas near Bonneville Dam (Ives, Horsetail, Multnomah and St Cloud spawning areas) look to have peaked late last week/early this week and numbers are better than last year in all areas, according to Hillson.

 

“The two mainstem Columbia River spawning areas near the I-205 Bridge (Woods and Rivershore) have significantly more adults present this year compared to previous years,” Hillson said. “Close to 800 adults were accounted for between the two areas when my seining crew was there yesterday.” The Interstate 205 bridge connects Portland, Ore., and Vancouver, Wash.

 

Hillson said that a communication with the Oregon Department of Fish and Wildlife’s Tom Murtaugh indicated that chum counts are substantially above average this year in rivers in Oregon such as the Tillamook, Necanicum and Nehalem.

 

The jury’s still out on the final return numbers, but it is already obvious that chum are taking a liking to the Hamilton spring channel, which this late summer-early fall was cleared of an overgrowth of canary grass and blackberry bushes, and overlain with fresh spawning gravels. It’s believed the vegetation cramped spawners and suppressed the upwelling of spring water that bubbles to the surface.

 

Gravel and, particularly slightly warmer spring water upwelling, draws chum spawners like a magnet.

 

The Lower Columbia Fish Enhancement Group completed much of a planned rehabilitation of the Hamilton Springs chum spawning channel by October. The Bonneville Power Administration and WDFW provided funds to supplement money provided by Washington’s Salmon Recovery Funding Board for the effort. The supplemental funding allowed development of a 580-foot extension, called the east channel, of the Duncan Springs spawning channel.

 

That doubled the available spawning area, and it is being used.

 

“They only place where they’re not spawning is where grass is growing out of the bed,” said Tony Meyer, LCFEG executive director. The LCFEG is a non-regulatory, non-partisan 501(c)(3) salmon recovery organization founded by the state legislature in 1990.

 

“They are spawning throughout the whole length of the channel,” said Peter Barber, project manager for the LCFEG. That is of particular importance because in prior years spawners tended to congregate in the upper area of the channel to build their redds. With little space, the fish build nests on top of nests on top of nests, which is not an ideal scenario.

 

The project was funded and implemented in large part “to give them room to spread out,” Barber said.

 

Meyer noted this year’s unexpected density of chum spawners in the lower portion of the channel which was considered a low priority for rehabilitation. He theorized that removing the gravels embedded with mud and reed canary grass allowed otherwise suppressed sources of upwelling groundwater to emerge, which the chum seem to prefer as spawning habitat.

 

Also the sheer volume of flow coming out of the new east fork channel helps move organics downstream and likely attracts more chum into the channel, he said.

 

And regardless of the overall strength of the run, the performance at Hamilton springs is exceptionally strong.

 

“If you compare the number of fish in the channel with the number of fish in other spawning areas, it’s a pretty high percentage,” Meyer said. He said that past studies indicate that chum seem to find each other if some of the fish have located a good spawning area.

 

Plentiful river flows have allowed the U.S. Army Corps of Engineers' Reservoir Control Center in recent days to maintain tailwater elevations and flows below Bonneville Dam for the chum salmon spawning period in a range from 11.7 to 12.5 feet, which translates to an average outflow of approximately 135,000 cubic feet per second. That’s an increase from the initial target elevation averaging 11.5 feet.

 

The elevation increase was requested by salmon managers to allow fish access to more suitable habitat at Ives Island, which is located just off the mouth of Hamilton. The elevation has been held at an average of 11.5 feet in recent years to limit spawning for areas below that elevation. In most years it is difficult to maintain tailwater elevations above that level through the winter, but river flows are, for the time being, strong.

 

“The likelihood of stepping it up is low,” NOAA Fisheries’ Paul Wagner said of the prospect of maintaining even higher tailwater elevations. The fish managers’ request, explained three weeks ago by Wagner at a meeting of the Technical Management Team, included a second step in operations that involved boosting the elevation to 13.5. But near-term forecasts for low precipitation may preclude that.

 

Meanwhile, “there’s not a lot of activity in the Ives area,” Wagner said. A survey conducted Nov. 22 by the WDFW estimated there were 38 chum spawners in the area.

 

Hamilton springs channel “is the place where chum have chosen to spawn,” Wagner said.

 

The outflow from Bonneville Dam may be adjusted higher during low tide and dry periods and lower during high tide and rain events in order to keep the tailwater elevation in a stable band, according to a Nov. 23 press release from the Corps’ Northwestern Division office. This season the outflows may be adjusted to as low as 58 kcfs, with flows of at least 77 kcfs at the confluence of the Columbia and Willamette rivers. 

 

By holding elevation and flows in a stable range during November and December, adult chum salmon will be able to dig nests, or redds, and more effectively use available habitat in the river and nearby creeks, said Doug Baus, fisheries biologist with the Reservoir Control Center. After December and until early spring, Bonneville Dam will operate to ensure established redds remain completely watered until juvenile chum emerge.

 

Since the National Marine Fisheries Service listed chum salmon as a threatened species in March 1999, Columbia River operations have supported fish spawning in the fall and the protection of chum eggs and the next generation of young fish until they migrate downstream the following spring.

 

Corps mainstem reservoirs also operate to reduce flood risk and meet spring salmon migration needs. 

 

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