Scientists use tags to track Columbia River salmon

Scientists are using acoustic tags to better understand how juvenile salmon and steelhead travel from John Day Dam on the Columbia River to the Pacific Ocean.

Researchers from the Pacific Northwest National Laboratory in Richland and the U.S. Army Corps of Engineers' Portland District are tagging about 240 fish each day over the next several weeks to study why some young fish survive the ocean journey and others perish.

The tagged fish will emit high-pitched beeps that can be picked up by underwater sensors as they approach and pass the dam near Rufus, Ore., the Tri-City Herald reported.

"It tells you how fast (the fish) is moving and which route it is taking," said Geoff McMichael, the PNNL's program manager.

The corps uses the acoustic tagging system as a primary tool to assess juvenile salmon survival in the Columbia River.

Researchers said the tags, which are smaller than pencil erasers and inserted into the belly of juvenile salmon, will help improve salmon passage at the dam.

"It allows us to select the best operation of the dam," balancing demands of fish, power and recreation, said Brad Eppard, a corps fisheries biologist.

Last year, after data showed gulls eating fish after they passed through the dam, officials hung long wires to keep the gulls away.

This year, researchers are evaluating temporary weir systems designed to direct fish away from dam turbines and get them through the dam safely. The corps is considering whether to place permanent weirs at the dam, and researchers are studying whether increasing water flow over two-day periods affects how many fish survive the trip down river.

The tag embedded in each fish emits a distinct code, allowing researchers to track individual fish.

About 200 detectors placed along the river pick up "pings" from the tags as the salmon approach the dam. Another set of detectors near the dam pinpoint where each fish is swimming.

Each transmitter has a battery that lasts 25 to 40 days. Fish that survive the journey to the ocean take about two weeks from John Day Dam.

Up to 97 percent make it through the dam, but only 75 percent to 85 percent reach the ocean.

Researchers are able to monitor a salmon's movements on a computer as the fish finds its way through a weir, a spillway, the powerhouse or the turbine bypass.

McMichael said the acoustic system detects 99 percent of tagged fish up to 300 yards. The lab developed the system for the corps in 2001.

PNNL will also tag and release fall chinook salmon at the dam later this summer.