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Supplementation Efforts Bringing Record Breaking Fall Chinook Counts To Lower Granite Dam
Posted on Friday, September 24, 2010 (PST)

The steady stream of fish passing over the lower Snake River's Lower Granite Dam this week bodes well for a doubling of the modern-day record return of fall chinook salmon.


The fall chinook adult count at Lower Granite for 2010 had reached 16,885 by Sept. 16. That was about 1.94 times greater than the 2009 count through that date and 3.38 times greater than the 10-year average, according to the Fish Passage Center's Sept. 17 weekly report.


The total through Sept. 16 already exceeded the modern-day record of 16,628 set in 2008.


The counts since Sept. 16 have remained strong, bringing the total to 24,791 adult fall chinook through Thursday when the daily count was 910. The peak daily counts this year were 1,799 on Sept. 12 and 1,715 on Sept. 18.


"It's a record by a long shot," Stuart Ellis, Columbia River Inter-Tribal Fish Commission biologist, said of this year's tally. The counts kept at Lower Granite since the hydro project went into operation in 1975.


The counts are starting to ebb but fishery officials expect count to reach at least 30,000 at Lower Granite, the eighth hydro project the fish hurdle during their spawning journey up the Columbia and Snake rivers before zeroing in on their points of origin.


By the time Lower Granite and other lower Snake hydro projects were built in the 1960s and 1970s, the wild Snake River fall chinook population was in a steep decline with passage to spawning habitat in the upper Snake blocked with the earlier construction of the Hells Canyon Complex and other dams upstream.


And the annual returns continued to shrink, totaling  as few as 383 fish, as counted at Lower Granite, in 1990. The stock was listed as threatened under the Endangered Species Act in 1992 and includes naturally produced fish from the Tucannon, Grande Ronde, Imnaha, Salmon and Clearwater rivers, as well as four artificial propagation programs: the Lyons Ferry Hatchery, Fall Chinook Acclimation Ponds Program, Nez Perce Tribal Hatchery, and Oxbow Hatchery fall-run Chinook hatchery programs.


A resurgence in recent years is due in large degree to the fall chinook acclimation project led by the Nez Perce Tribe that began in 1996. The program involves bringing hatchery produced juvenile fish to three "acclimation" sites -- two on the lower Snake and one on the Clearwater River -- for their final rearing before release. The sites are located near major natural spawning areas.


The effort is aimed at supplementing the natural spawning effort by acclimatizing the young hatchery fish along the river so they home in on those areas when they return as adults to spawn.


The returns are from naturally spawned fish as well as the product of the state of Washington's Lyons Ferry Hatchery, the Nez Perce Tribal Hatchery and the Idaho Power Company. A major source of the growth has been the supplementation effort.


"We've been seeing some growth that is gangbusters," said David Johnson, head of the NPT's Department of Fisheries Resources Management.


A big return was expected -- as many as 60,000 adult fish -- based in part on a record return of "jacks" last year. Jacks are young fish that return to freshwater after only a year in the ocean. Their number helps to gauge the number of their broodmates that might return during the following 2-3 years.


The jack count at Granite in 2009 was 41,285, which was four times the next highest total on record.


Favorable ocean conditions may have helped improve survival as the fish grew to maturity.


"Another big factor is that we've finally reached our full production" goal for streamside acclimation and release, said Becky Johnson, deputy director of the tribe's Production Division.


"We're just getting returns this year from the full 5.9 million" production target that was first achieved two years ago, Ellis said. Those subyearling and yearling fish are released either on-site at Lyons Ferry Hatchery or at the acclimation sites.


It has not been determined yet how many of the returning fish are truly "wild" fish -- fall chinook that were actually born in the spawning gravels of the Snake and its tributaries. Over the past seven years from 9.5 percent (2009) to 33.5 percent (2006) of returns, as counted at Lower Granite, have been naturally produced. The preseason forecast was for a return of 5,300 wild Snake River fall chinook to the mouth of the Columbia River.


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