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Sunday, March 18, 2018

Red dye study examines Yellowstone River flow

USGS research geologist Dr. Susannah Erwin, right, and ecologist Ed Bulliner watch from the back of their boat as they deposit Rhodamine WT water-tracing dye into the Yellowstone River downstream from Glendive on Thursday. The scientists were studying how the dye plume dispersed and drifted down the river to help them better understand the river’s hydrology, particularly how the currents affect fish larval drift.


By Jason Stuart

Ranger-Review Staff Writer

The Yellowstone River turned red on Thursday downstream from Glendive, but it was no biblical plague invading the river, but rather an experiment conducted by government scientists in order to better understand the lower Yellowstone’s hydrology and specifically how larval fish drift through that section of the river.

Thursday’s river dye experiment was undertaken by scientists from the U.S. Geological Survey, most of whom came up for the occasion from the USGS’s Columbia Environmental Research Center in Columbia, Mo. Leading the dye experiment was USGS geologist Dr. Susannah Erwin. Also involved in the effort was Dr. Pat Braaten, a USGS research biologist stationed out of Ft. Peck who is one of the government’s leading experts on the endangered pallid sturgeon.

Braaten noted that while the research the USGS is conducting on the Yellowstone is not solely for pallid sturgeon, the study is definitely “all tied together” with the ongoing effort to save the endangered fish by providing them with a way to move upstream of the Intake diversion dam structure.

Erwin cut across the river in a channel about 4 miles downstream from Glendive, releasing the non-toxic red dye Rhodamine WT into the river from a large barrel in the back of her boat. Other USGS researchers downstream then monitored how the dye plume moved through and down the river, which the scientists are hoping will provide them with a better idea of how larval fish — including pallid sturgeon — will drift through the Yellowstone. 

The USGS actually conducts hydrology tests on the Yellowstone in the Glendive area every summer, though the dye test was something new. Braaten noted that the hydrology data the USGS has gathered on the Yellowstone upstream of Intake in previous summers has already had an impact on the design plans there, as that data “actually fed directly into the design of the side channel.”

As the USGS expert on pallids, Braaten had some interesting tidbits to share about the fish, though he noted the species remains little understood by scientists.

“In the pallid world, you think you’re getting them figured out and then they throw you a curveball,” Braaten said.

One interesting thing Braaten noted is how relatively few of the adult pallids actually run all the way up the Yellowstone to Intake. He said in most years, only 12-18 percent of wild, adult pallids make a spawning run up the Yellowstone to Intake. The rest of the wild adult pallids tend to hang around not too far from the confluence with the Missouri, being, for lack of a better term, ‘lazy.’

“You know, it’s really interesting. You have a group of fish and most of them hang around in that Fairview area, but then you have some others that really have that motivation to run,” Braaten said.

He added that pallids are not necessarily unique amongst fish species in having some individuals very motivated to make spawning runs while others lay around and take it easy.

“It’s not so uncommon to find what you might call a partial migration population,” Braaten said.

River conditions can and do change that behavior, however. Braaten noted that in 2011, which was a “record flow year” on the Yellowstone, 26 percent of the wild pallids made a spawning run up to Intake.

“Those higher flows get ‘em motivated to go,” he said.

Getting those wild pallids that run up to spawn around Intake so they can do so successfully is the entire purpose of the diversion dam replacement project proposed by the U.S. Army Corps of Engineers and the Bureau of Reclamation. Scientists widely believe that as it currently stands, the larval pallids do not have enough river miles from Intake to drift and develop before they ultimately flow into the clear, oxygen-starved waters of Lake Sakakawea in North Dakota, where the conditions make them highly susceptible to simply dying off or being eaten by predatory fish.

When the water is high enough, as it is right now, Braaten noted that some pallids do occasionally find their way around Intake.

“When the flows get up to that 35,000 cfs range, then that natural side channel (at Intake) starts flowing and fish will use that if they find the entrance,” he said.

He added the one documented occurrence of wild pallids spawning above Intake happened in 2014, when one female and several males followed the natural side channel around Intake and moved all the way up to the Powder River, where the female spawned.

That incident of course begs the question of whether or not pallids will use the artificial bypass channel the Corps is proposing to build at Intake to provide fish passage around the diversion dam, which itself would be replaced with a concrete weir with a 150-foot wide ‘fish notch’ cut into the center of it to provide further fish passage opportunities in high water periods. A pair of environmental groups have filed lawsuits in federal court seeking to block the Corps’ plan at Intake, arguing that the pallids won’t use the artificial channel.

Asked point-blank if he thinks pallids will use the artificial side channel, Braaten replied that while the evidence seems to suggest that they would, there’s no way of knowing until they do.

“Let’s put it this way ... we see ‘em use side channels,” Braaten said. “Now will they use a constructed side channel? That’s a tough call.”

Reach Jason Stuart at rrreporter@rangerreview.com.

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