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River Flow Regime Set To Protect Listed Chum Salmon Spawning Below Bonneville Dam
Posted on Friday, October 29, 2010 (PST)

With an unknown number of chum salmon known to be headed up the Columbia River, the Technical Management Team on Tuesday set Nov. 1 as the date for the start of flows past Bonneville Dam at levels designed to facilitate spawning and protect egg nests until young fish hatch out next spring to start a new generation.


The Columbia River chum salmon stock has since March 1999 been listed as threatened under the Endangered Species Act. The two primary chum population centers are located in the Grays River area in the lower Columbia estuary and below Bonneville Dam in Hamilton Creek, Hardy Creek in Washington, and nearby at Ives Island and Pierce islands. Bonneville is about 146 river miles from the mouth of the Columbia.


The May 2008 Federal Columbia River Power System biological opinion says to provide a tailwater elevation below Bonneville Dam of approximately 11.5 feet beginning the first week of November (or when chum arrive) and ending by Dec. 31, if reservoir elevations and climate forecasts indicate that operation can be maintained through incubation and emergence. That tailwater elevation allows fish access to tributary spawning and then keeps eggs underwater until they hatch in the spring. The NOAA Fisheries BiOp describes measures the agency feels are necessary to avoid jeopardizing the survival of listed salmon and steelhead stocks.


Daytime flows are expected to be approximately 120,000 cubic feet per second to achieve this tailwater elevation, but may range higher or lower depending on contributing factors such as tidal effects or unexpected inflows, according to Doug Baus, fisheries biologist with the U.S. Army Corps of Engineer’s Reservoir Control Center. The Corps operates Bonneville and, along with the Bureau of Reclamation, other dams in the Columbia-Snake river system.


NOAA Fisheries’ Paul Wagner said TMT members agreed on a strategy in which the hydro system would be operated to assure a tailwater elevation of at least 9.5 feet for the last five days in October before moving to the BiOp prescribed elevation.


The chum operation can threaten the system’s capability to store desired amounts of water for other fish-related actions, such as the provision for stored water to augment flows for spring salmon migrations. But, most forecasts for the winter of 2010-2011 point to prevailing La Nina climatic conditions, which tip the odds toward higher than average precipitation in the Pacific Northwest.


The Corps reservoirs are also operated to prepare for winter flood control.


Recent storm events and higher flows appear to have cued chum into earlier-than-normal spawning behaviors, said Baus. Precipitation as measured above The Dalles for the month of October to date is 123 percent of normal.


Monitoring in place since 1998 shows that the first arrival of live chum at the Ives Island spawning grounds ranged from as early as Oct. 23 (last year) to as late as Nov. 14. As of Tuesday no chum had been spotted at Ives or any of the upriver – from the Interstate 205 bridge at Portland up to Bonneville – sites.


Chum have been appearing in the catches of the lower Columbia gill-net fleet since an Oct. 5-6 fishery. And that chum presence has been big, relatively speaking.


“We’ve seen a lot of fish caught in the gill-net fisheries,” Wagner said. Generally the appearance of chum on the Ives Island and other nearby spawning areas comes within a few weeks of their appearance in the lower river.


Another sign that the chum return may be higher than average number – 22 – that have already been counted in Bonneville Dam’s fish ladders. Wagner said that this point in time typically fewer than 10 chum would have been counted.


A total of 247 chum have been netted this year. That’s the most since 1992 when gill netters landed 700. The next highest total during that period was 116 in 2001. The vast majority of the chum catch was during fisheries staged in the mainstem from Longview, Wash., down to the river mouth.


“In recent years the numbers (of chum caught in commercial fisheries) have been pretty small, and we have changed out fishing practices” to avoid incidental take of listed chum, the Washington Department of Fish and Wildlife’s Cindy LeFleur said. The WDFW and Oregon Department of Fish and Wildlife co-manage Columbia mainstem commercial fisheries, which no longer extend into November when the bulk of the chum spawners arrive. Harvest management agreements allow an impact of as much of 5 percent on any year’s chum run, but the state agencies manage fisheries to hold impacts below 2 percent, LeFleur said.


“The numbers have been so small that we haven’t had to worry about it,” LeFleur said of the minimal sport or commercial chum catch in recent years.


The most live chum counted at the Ives Island/Pierce Island spawning areas was 1,157 in 2002, according to data posted online by the Fish Passage Center. That record goes back to 1998. Second most was 298 in 2003.


The annual historic run size to the Columbia River was estimated to be 1,392,000 chum salmon, according to information posted on the WDFW’s web site. The current run size is less than 3 percent of historic run size, and is less than 12 percent of the 1951 run size, the WDFW says.


Observations of chum salmon still occur in most of the other 13 basins/areas that were identified in 1951 as having populations. But returns to those areas are extremely small, LeFleur. The Grays system has by far the Columbia River chum population.

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