the film
Commentaries and editorials

Sources Of Mortality
for Snake River Fall Chinook

by Fred Mensik
Columbia Basin Bulletin, July 28, 2006

In the 7/21/06 CBB, Michael Garrity uses statistics as part of his pro-breach agenda that require clarification.

bluefish often points visitors to 2000 Biological Opinion data at dampool.htm that will be useful for the following discussion. Note the high mortality in the uppermost reservoir before collection for transportation occurs downstream at Lower Granite Dam. In 2000, this region of mortality was considered (by Marvier et. al.) to be a part of the "first-year mortality" of juvenile salmonids.

Mr. Garrity states, "The 2004 Biological Opinion found that the hydrosystem kills an average of 49-86 percent of outmigrating juvenile salmonid and steelhead (depending on the species)."

The 86 percent statistic Mr. Garrity uses refers only to in-river Snake River fall chinook, the majority of which are hatchery production fish that have a higher mortality rate than their wild counterparts.

These fall chinook migrate when river flows are diminishing and river temperatures are at their highest. When water temperatures reach 70 degrees Celsius, the bacteria columnaris infects fall chinook and many in-river fall chinook die from this bacteria before they reach the ocean. High water temperatures and diminished flows would come into play even if the dams did not exist on the Lower Snake River.

Also, 40 to 50 percent of hatchery reared fish (depending on the species and release distance from Lower Granite Dam) die in the hydro system before they reach Lower Granite Dam. This mortality starts as soon as hatchery fish are released into tributaries upstream of Lower Granite Dam and continues as they migrate to the ocean. This mortality rate is the nature of hatchery fish and should not be entirely associated with the existence of dams built for fish passage.

Additionally, 75 to 80 percent of the fish are transported (2004 Biop) and barge mortality from Lower Granite, Little Goose, Lower Monumental and McNary Dams is less than 0.1 percent. The 49 to 86 percent statistic may be correct, but coming from a breach advocate, one might infer that 100 percent of these mortality statistics is caused solely by dams. This is simply a misunderstanding of the statistic.

In the last sentence of his fourth paragraph, Mr. Garrity states, "And lower Snake dam removal would more than double available mainstem spawning habitat for Snake River fall chinook." Although the statistic may be correct, the statement needs a reality check.

"Fall chinook were widely distributed occupying the mainstem Snake River and the lower reaches of its major tributaries, upstream to Shoshone Fall, Idaho. The upper reaches of the River were the primary area utilized by fall chinook with only limited spawning activity reported downstream from fiver kilometer (Rkm) 439 (downstream from Hells Canyon." (Draft Snake River Salmon Recovery Plan Recommendations, October 1993). From this description of historic fall chinook distribution, it is recognized that limited spawning occurred below Hells Canyon and that even fewer fish historically spawned in the lowest reaches of the Snake River where the Lower Snake River dams exist.

Fisheries Biologist Ted C. Bjorn wrote, "The fall chinook salmon runs that enter the Columbia River and Idaho have experienced a general decline in numbers. Elimination of the commercial fishery above Bonneville Dam has increased the upriver escapement. However, water resource development, including dam construction, has reduced the amount of spawning area in the Snake River in Idaho to only 25 per cent of its former abundance" (The Salmon And Steelhead Stocks of Idaho, State of Idaho Department of Fish and Game, March, 1960). Mr. Bjorn wrote this research paper in 1960, prior to the completion of Ice Harbor Dam, the first of the Lower Snake River Dams, and is identifying the Hells Canyon Complex impact on fall chinook habitat.

During a smolt workshop in 2000, a Battelle representative talked about the results of substrate samples taken above Brownlee reservoir, stating that predicted estimates of mean egg survival at the Snake River substrate sample sites taken above Brownlee reservoir equaled or exceeded estimates from fall chinook salmon spawning areas in the Hanford Reach. In other words, if adult fall chinook could once again have access to these spawning grounds above Brownlee Dam, this stretch of the Snake River could potentially produce more fish than the Hanford Reach. (Hanrahan TP, DR Geist, and EV Arntzen. 2005. "Habitat quality of historic Snake River fall Chinook salmon spawning locations and implications for incubation survival: part 1, substrate quality." Rivers Research and Applications 21(5):455-467.

In 1953, before the construction of Ice Harbor, the first of the four lower Snake River dams, Forrest R. Hauck, fishery biologist for the Idaho Department of Fish and Game wrote, "The controversial Hells Canyon issue doesn't look so bright. Either Hells Canyon dam (over 600 feet high) as proposed by the Bureau of Reclamation, or the series of three dams (with a combined heighth (sic) of over 600 feet and Brownlee exceeding 300 feet) will prevent the upstream passage of fish. At least there are no known, successfully-operating fish-ways over 100 feet high. These dams, if constructed, will stop the runs of steelhead up the Snake and Weiser rivers, the spring chinooks up the Weiser, and the fall chinooks up the Snake River. Future high dams, proposed on the Clearwater, Snake and Salmon rivers may further deplete or destroy Idaho runs of migratory fish." (Idaho Wildlife Review, The Salmon and the Steelhead, July-August 1953).

Yet, Mr. Garrity suggests we remove four Lower Snake River dams to double what is clearly identified as the poorest, least productive and the least used fall chinook spawning habitat, with the assumption that this will develop a self-sustaining fall chinook population.

The history of salmon and salmon habitat destruction in the state of Idaho that caused fish number declines before the Lower Snake River dams were built is well documented. Knowing this history allows one to more accurately identify where viable historic spawning habitat existed and to recognize what Idaho Biologists like Forrest Hauck and Ted Bjorn recognized...that dams without fish ladders are fish species killers.

There are no fish ladders in the state of Idaho. Lower Snake River dams have fish ladders. If you remove Lower Snake River dams, you still have the Idaho problem.

To have healthy, self-sustaining anadromous fish populations, adult fish must have access to an adequate volume of quality spawning grounds. This is just basic fish biology. Mr. Garrity and I are in agreement in our desires to have healthy, self-sustaining populations of Snake River salmon. How to achieve this goal is where we diverge and why it is so important to scrutinize the broad brush sound-bites of pro-breach advocates.

bluefish would like to remind website visitors that Idaho's wild Sockeye, Spring/Summer Chinook and Summer Steelhead face no dams in Idaho with the exception of Dworshak Dam on the North Fork of the Clearwater River and the Hells Canyon Complex on the mainstem Snake. Keep in mind that the Salmon River is the longest undammed river in the lower 48 states. The Salmon River drainage alone historically produced about 45% of the Spring/Summer Chinook in the entire Columbia River drainage. It continues to support huge amounts of high quality habitat essential to wild Spring/Summer Chinook and Summer Steelhead recovery.

The Snake River drainage presently available to salmon and steelhead - the Clearwater and Salmon rivers in Idaho, the Grand Ronde and Imnaha rivers in Oregon and Washington and the Tucannon river in Washington - supports thousands of miles of Spring/Summer Chinook and Summer Steelhead habitat that is going unoccupied by the anadromous species. The Snake River drainage historically produced 55% of the Summer Steelhead in the entire Columbia drainage.

Fall Chinook salmon used to range 645 miles up the Snake River to Shoshone Falls but are now limited in the mainstem Snake River from the head of Lower Granite Reservoir to Hells Canyon Dam and the lower Clearwater River - about 140 miles of habitat. A robust population of Fall Chinook can be found in the Mid-Columbia's Hanford Reach just above the Lower Snake River confluence with the Columbia to Priest Rapids Dam.

Fred Mensik Pomeroy, Wash.
Sources Of Mortality For Snake River Fall Chinook
Columbia Basin Bulletin, July 28, 2006

See what you can learn

learn more on topics covered in the film
see the video
read the script
learn the songs
discussion forum
salmon animation