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Scientists Listen for Sound of Salmon by Associated Press Seattle Post-Intelligencer - August 4, 2003

PORTLAND, Ore. -- A new tracking system at the mouth of the Columbia River is allowing scientists to study how dams are affecting threatened and endangered salmon.

Until now, no one has been able to track what happens to salmon during their final migration to the sea once they pass Bonneville Dam, almost 150 miles upriver.

The federal government spends more than $700 million a year in the Columbia River Basin to sustain and rebuild salmon runs. The spending, however, has not turned things around for many stocks, particularly those bound to the farthest upriver reaches of the Snake River, past eight large hydropower projects.

The Corps of Engineers, which runs the Columbia's extensive system of hydroelectric dams, spent close to $2 million to develop the new tracking system, The Oregonian reported in its Wednesday's edition.

To track the fish, biologists suspended two rows of automated electronic sensors, called hydrophones, to listen for baby salmon passing by. The sensors pick up recorded pinging signals sent from transmitters implanted in a thousand smolts.

"We'd like to know how much mortality is due to travel through the hydropower system, then try to manipulate the system to reduce the causes of that mortality," said Lynn McComas, a fisheries biologist with the National Marine Fisheries Service.

The detectors float about 15 to 25 feet below the surface of the river and about 15 feet from the river bottom, tethered to a heavy steel anchor.

"We have detections from several hundred fish, of the 923 released, and have some great new insights about how long it takes these fish to get to the ocean from Bonneville Dam," said Geoff McMichael of the Battelle Pacific Northwest National Laboratory in Richland, which helped develop the system.

Based on a preliminary analysis, he says juvenile chinook take about three days to make the trip. The trial run also shows its possible to pinpoint where in the river channel fish migrate, and how tides and daylight affect their entry into the ocean.

Assuming funding comes through, the researchers expect to place a larger set of hydrophones next year and complete a full survival study on juvenile chinook salmon from Bonneville Dam to the ocean.

"At the end of all this, we'll have a monitoring function to see how change in the management of the hydro system and changes in hatchery releases affect survival in the lower river," McMichael said.