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Snake River Fall Chinook Spawn in Record Numbers

by Mike O'Bryant
Columbia Basin Bulletin - January 31, 2003

The number of fall chinook redds found this year at Snake River sites is the largest since Idaho Power and the U.S. Fish and Wildlife Service began surveying redds in 1991. The utility and agency, surveying the mainstem river, as well as the Grande Ronde, Imnaha, Salmon, Potlatch and Clearwater rivers, found a total of 1,851 redds.

Most of those -- 1,113 redds-- were located by airplane or underwater cameras in the Snake River downstream from the utility's Hells Canyon Dam. Last year they found 710 redds along that reach of river.

Idaho Power fisheries biologist Phil Groves attributes the rising number of redds to good water three years ago, a hatchery supplementation program by the Nez Perce Tribe at the Lyons Ferry Hatchery, better ocean conditions and stable river flows from the dam that ensure the redds remain watered.

"By providing stable spawning flows in the Snake River, we eliminate potential redd losses and prevent the embryos from drying out," Groves said.

When Idaho Power built nearly 50 years ago the three dams that make up the Hells Canyon Complex of Dams -- in order from downstream, they are Hells Canyon, Oxbow and Brownlee dams, accounting for 60 percent of the utility's (hydroelectric) electricity generation (see Idaho Power 2001, more than half is coal-fired)-- they effectively blocked much of the historic habitat where fall chinook spawned. Today spawning for those fish is limited to about a 50-mile stretch of mainstem river below Hells Canyon Dam and tributaries.

Wild fall chinook were listed by the National Marine Fisheries Services as threatened under the federal Endangered Species Act in April 1992 after their numbers reached a low of 79 spawning fish in 1990. Idaho Power initiated the salmon flow in 1993 to improve spawning conditions as a response to the listing. Last year it set the flow Oct. 14 at a flat 8,700 cubic feet per second, 24-hours a day, and held the flow constant until early December.

This week flows out of the Hells Canyon Dam were at 19 kcfs, according to Dennis Lopez of Idaho Power. He said the utility is committed to maintaining a minimum flow of 8.7 kcfs (the spawning flow) through the time the eggs hatch and the fry emerge from the nests sometime this spring.

Not all of the spawning fish are wild. Some are first generation hatchery fish from the Washington Department of Fish and Wildlife-operated Lyons Ferry Hatchery near Lower Monumental Dam.

Even the water supply forecast at Brownlee Dam of 56 percent of normal won't affect the operations, he said. The U.S. Weather Service's River Forecast Center is predicting April--July inflow into Brownlee Reservoir will be 3.53 million acre-feet, while the normal inflow is 6.3 maf. The greatest demand placed on that water is for generation in July, Lopez said, long after the emergence is complete. He would not predict, however, how the low water supply forecast will affect flow augmentation this summer.

Related Sites:
Idaho Power:

From Phil Groves, Idaho Power Company biologist:

The following information is in response to CBB, Jan 31 2003, Story No.4, SNAKE RIVER FALL CHINOOK SPAWN IN RECORD NUMBERS.

I am IPC biologist Phil Groves, and would like to clarify some items in this article.

First of all, the redd surveys along the Snake, Grande Ronde and Imaha rivers are jointly conducted by the IPC and USFWS; surveys along the Clearwater, Salmon and Potlatch rivers are conducted by the Nez Perce Tribe - I am certain that they would like credit for the work they do.

Also, all of our aerial surveys are conducted from a helicopter - not a fixed-wing airplane. Our underwater searches use a remotely operated underwater video system, and those searches were begun in 1993 and are only conducted within the Snake River by IPC and the USFWS.

The Nez Perce Tribe supplementation program has been using fish supplied by the Lyons Ferry Hatchery (part of the Snake River fall chinook salmon ESU); however their program does not occur at the hatchery, but at NPT satellite facilities located at Pittsburg Landing and Billy Creek on the Snake River, and at Big Canyon on the Clearwater River. Also, their program is being significantly expanded, and it may be very much worth your while to actually contact them and do a separate article on their activities (contact Dave Johnson, NPT 208-476-7296).

It is very important to note that spawning presently occurs along 100 miles (not 50) of the free-flowing Snake River (between the Hells Canyon Dam and the town of Asotin, Washington), as well as along extensive stretches of the lower river tributaries - especially the Clearwater, Grande Ronde, and Imnaha rivers.

In 1990, the number of fall chinook adults allowed to actually pass upstream of Lower Granite Dam and spawn totaled approximately 335, of which approximately 75 were deemed to be "wild" Snake River fall chinook.

Finally, IPC began its protective flow program during the spawning season of fall 1991, not 1993.


Phillip A. Groves
anadromous fishery biologist
Idaho Power Company
(208) 388-2597

Mike O'Bryant
Snake River Fall Chinook Spawn in Record Numbers
Columbia Basin Bulletin, January 31, 2003

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