the film
Economic and dam related articles

Strobe Light Results Favorable

by Stephen Mercer
The Star of Grand Coulee - October 1, 2003

Tentative results show kokanee repelled by strobe light

A flash of light at the forebay of Grand Coulee Dam's Third Powerhouse could serve as a stop sign for fish going through the dam's turbines.

This summer, scientists conducted tests and collected and studied data to find out if flashing strobes of light elicit negative reactions in fish, especially kokanee, to prevent them from being sucked down the Columbia River through the dam's turbines.

That was the goal of the approximately two-month experiment that ended last month.

This year marked the third year of the program, said Richard LeCaire, project manager for the Tribes' Chief Joseph Kokanee Enhancement Project. He said the annual $1.36 million project, funded by the Bonneville Power Administration, will conclude next year.

The project counted 1.65 million fish as being "entrained" - or going in and out of 14 of the 24 turbine intakes.

LeCaire said they had "concluded that entrainment was a major problem at the dam."

In the past, the Bureau of Reclamation said they might install the strobe lights at the dam if they are shown to work.

Bureau Public Affairs Officer Craig Sprankle said the agency still would need to look at "the big picture," including test results and where the strobe lights would need to go, before making any decisions.

The BPA also funds the fish hatcheries where many of the fish are raised on Lake Roosevelt. LeCaire said they do research on those fish raised in the hatcheries, but the main focus is those born in the wild.

He said this year's tests and the tests from the last two years, which also included rainbow trout, appear to show that kokanee are affected by the strobe lights and the trout are not.

But the project "still hasn't come to (any) conclusion" on the effects of the strobes, LeCaire said.

The project includes Grand Coulee Dam and Chief Joseph Dam near Bridgeport, because of mitigation to compensate for the loss of fishing opportunities to everyone due to the construction of the dams.

This year tests were set up with barges in a new location alongside the third powerhouse, from which lights flash and sensors listen to the behavior of the kokanee.

Beneath one barge, six 1,000-watt strobes flash 360 times a minute, supposedly annoying the fish with a curtain of light. The number of fish coming by is measured by sophisticated hydroacoustic equipment on another barge that "pings" the water 20 times a second.

And 200 kokanee, the highest number yet, have had tiny transmitters surgically inserted into their guts above and below the dam. Another set of eight underwater listening devices received those signals.

All of the data were transmitted to a bank of computers and instruments in a small trailer parked on the Third Powerhouse. Much of it can also be transmitted via the Internet to Tennessee, the headquarters of Flash Technology, which makes the strobes, and to Richland, Wash., to Pacific Northwest Laboratories.

The data from those tests is still being studied, LeCaire said.

To help provide expertise for the project, scientists from an independent scientific review panel have also been involved.

He said the strobe light technology was first shown to work at Dworshak Dam in Idaho, where the fish retreated after seeing the light.

But Grand Coulee Dam posed different challenges than Dworshak.

A large amount of water being pumped while the fish were near the dam may have prevented them from responding to the light, LeCaire said.

Many of the large fish also showed up as the test was ending, so he said next year the test will end later in August to count those fish.

The strobe light test is just one of the project's objectives, LeCaire said. They also will study the entrainment of fish in the Banks Lake pumping station.

He said no formal tests have been done on the Banks Lake pumping station yet, but he knows entrainment occurs. The actual tests will be conducted next year.

Stephen Mercer
Strobe Light Results Favorable
The Star of Grand Coulee, October 1, 2003

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