On the northern panhandle of Idaho, the Kootenai River’s endangered white sturgeon are getting help from scientists who are “listening” to the river. A U.S. Geological Survey team is using soundwaves to learn how sediment is building up and affecting the fish’s ability to reproduce.
Every river has sediment. It’s the sand, gravel and general muck that rolls along with the current. Sediment can be both good and bad for a river.
“It’s good in that sediment can promote natural changes in the movement of a river and can provide habitat for certain species,” Molly Wood, USGS hydraulic engineer, says.
But for endangered white sturgeon, all that sediment has been harmful, covering up the eggs they lay.
White sturgeon were once abundant in the Kootenai River, which flows from its headwaters in British Columbia through Montana and Idaho and back into B.C.
Since the start of the 20th century, mining, logging, agricultural runoff and the construction of dams, dikes and levees along the river have led to the collapse of the sturgeon population. Things got worse after 1975 when the 3,000-foot-wide Libby Dam was completed in Montana.
By 1994, this prehistoric fish was added to the federal government's list of endangered species.
At one time, white sturgeon were so plentiful here that the people of the Kootenai Tribe of Idaho relied on them as a major source of food. Tribal people used to catch fish, which can often reach more than 10 feet, using huge basket traps and wicker weirs.
Now, with only about 1,000 wild sturgeon left in this stretch of the river, the tribe is trying to bring them back from the brink of extinction.
"There really wasn't any program being put into place so we stepped in and said, why don't we do something," said Ronald Abraham, a member of the tribe's council.
The tribe is working with the USGS to take soundings of the river. And that is providing scientists with important clues about where sediment is accumulating at levels that threaten white sturgeon eggs.
The USGS's Wood said scientists submerge devices that emit sound pulses into the river at specific frequencies, similar to sonar. The sound pulses reflect off sediment suspended in the water. Scientists use the strength of the return signal, called "backscatter," to calculate the amount of sediment particles.
"The use of acoustic technology is improving how we monitor sediment nationwide," Wood said.
Idaho was one of the first states to use this technology, but now USGS has deployed these acoustic monitors at about 40 sites across the country, including on the Snake and Elwha rivers in the Pacific Northwest and along the Mississippi River in the Midwest.