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Pallid sturgeon passage: New dam bypass on Yellowstone River luring fish upstream

The 40-foot wide bypass channel is filled with groundwater in this photo from last August. In April the channel was opened to flows from the Yellowstone River.  (BRETT FRENCH, Billings Gazette)
The 40-foot wide bypass channel is filled with groundwater in this photo from last August. In April the channel was opened to flows from the Yellowstone River. (BRETT FRENCH, Billings Gazette)
By Brett French The Billings Gazette

This spring, endangered pallid sturgeon wasted no time swimming up the newly opened bypass channel around Intake Diversion Dam on the lower Yellowstone River.

The two-mile long channel about 17 miles northeast of Glendive was flooded for the first time in late April. As of May 17, nine tagged pallid sturgeon swam through the passage, according to David Trimpe, a U.S. Bureau of Reclamation fish biologist. Three were wild male fish with the rest hatchery raised. Some of the hatchery fish were too young when tagged to identify as male or female.

Trimpe said it was a sign of success to see sturgeon using the channel.

“It was a pretty emotional week seeing those first few fish swim through the channel,” he said, especially after 20 years of work.

“It’s been a long time coming,” he added, praising the partnership with other state and federal agencies, as well as the irrigation district, for making it all possible.

Big bucks

The bypass channel is part of a $50 million project, which included increasing the height of Intake Dam. The dam diverts water into the 71-mile long Main Canal that provides irrigation water to about 55,000 acres on 500 farms in Eastern Montana and western North Dakota.

The bypass channel was designed to allow fish a way around the dam after its height was raised. With the channel working, fish have access to another 160 miles of the Yellowstone River as well as the mouths of the Tongue and Powder rivers.

The engineering project to create the channel was unlike any other because of its size and the fact that it was installed on an undammed river capable of high flows and destructive ice jams.

Although all species of fish will benefit from the new route around the dam, it was specifically designed to allow pallid sturgeon to swim upstream and successfully spawn – something that has been difficult ever since Intake Dam was built in 1905. The dam led to the decline in the fishes’ population, a species that can trace its ancestors back 78 million years. Pallid sturgeon were listed as an endangered species in 1990.

Trimpe said there are only about 100 wild fish alive in the lower Yellowstone and Missouri River below Fort Peck Dam. Another 7,000 to 8,000 hatchery fish – produced from eggs and milt taken from area fish – are believed to live in the same stretch of water. Out of these, about 200 to 300 are tagged.

Typically, only sexually mature fish will move upstream to spawn. That’s been about 12% to 26% of tagged fish stacking up below Intake Dam in the past, Trimpe said. Unfortunately, a lot of the wild fish have been spawning within the first 10 miles of the river, upstream from its confluence with the Missouri River, he added. That’s one reason the Army Corps of Engineers has studied imitating springtime runoff from Fort Peck Dam to entice the fish to move farther upstream to spawn.

Snowmelt

Likewise, runoff is what moves fish like pallid sturgeon and paddlefish below Intake Dam up the Yellowstone River. Right now, the Yellowstone is flowing at about 9,230 cubic feet per second, almost half its usual flow for this time of year.

“We’d really like to see a mature female pallid using the bypass channel,” Trimpe said.

It typically takes bigger river flows to entice egg-laden female sturgeon upstream.

The bypass channel, which now has a gauge installed, is flowing at about 2,200 cfs, Trimpe said. The waterway is built to handle about 20% of the main river’s flow, or up to about 20,000 cfs before the surrounding Joe’s Island is flooded.

“That’s the interesting thing we’re seeing this year, we’re getting a lot of fish moving upstream” despite the low flows, Trimpe said.

That may be due to the Powder River running at higher flows than usual, he speculated. In mid-May the flows on the Powder spiked to around 2,500 cfs, which may have lured fish upstream. Since then, the river has dropped to about 700 cfs.

Netting operations below Intake Dam over the past five years have moved about 50 to 60 pallid sturgeon above Intake Dam and about 20 to 30 have decided to stay upstream, most of them hatchery fish, Trimpe said.

“Which is good, because if they stay upstream they have a head start to move farther up,” he added.

Getting as far upstream as possible before spawning is believed to be key to the fish successfully reproducing. That’s because their larvae drift downstream after hatching. If they hatch too low in the river, the larvae die after floating into the oxygen-depleted sediments at the head of Lake Sakakawea. The same situation occurs on the Missouri River above Fort Peck Reservoir.

Studies have estimated pallid sturgeon larvae may need from 150 to 300 miles of river to drift before they mature enough to survive. The drift distance is dependent on river flows.

Past research has documented pallids successfully spawning in the Powder River and Yellowstone River near Miles City, Trimpe said. Whether or not those larvae survived, however, has not been documented.

“That doesn’t mean that they aren’t out there,” he added.

Paddlefish

Whether the new bypass channel will affect the paddlefish snagging fishery below Intake Dam is still uncertain. At the end of last week, four paddlefish with transmitters had moved through the bypass channel, according to Mike Backes, Montana Fish, Wildlife & Parks Region 7 Fisheries manager in Miles City.

“I’m guessing they will continue to move upstream, reducing any big concentration at Intake until a large pulse of fish arrives with much higher river flows,” he said in a statement.

“River flows aren’t adequate for a mass migration yet,” he added, although FWP caught one male paddlefish two miles downstream from the Powder-Yellowstone confluence on Wednesday while netting for shovelnose sturgeon.

The paddlefishing season opened on the Yellowstone on May 15. Backes said he’s heard little grumbling about whether the bypass channel will affect the fishery because most anglers aren’t aware it exists. Trimpe said he’s talked to boaters excited about using the channel to navigate up and down the river. The side channel could also spread out the paddlefishing activity, similar to what already exists on the Missouri River above Fort Peck Reservoir, he said.

The Intake Paddlefishing/Yellowstone Caviar Facebook page published photos of two large paddlefish caught on May 18, including a 107-pound female.

Montana Fish, Wildlife & Park’s harvest report showed a season total of eight fish taken at Intake, with 15 caught farther downstream, as of May 17. It’s estimated another six fish were caught that went unreported. Out of the fish caught, 15 were males and eight were females.

Caviar

Since 1991 the Glendive Chamber of Commerce has run a free fish cleaning station at the Intake fishing access site. In return for cleaning the fish, the chamber sold the paddlefish eggs to caviar buyers. The almost $1 million raised went into a variety of public projects in the surrounding counties.

“So it’s done a lot of good,” said Terra Burman, chamber executive director.

The chamber announced on the Facebook page that it will not be collecting eggs this year or at any time in the “foreseeable future” because the commodity price has dropped due to “China flooding the market” with caviar. Consequently, this will be the last year the chamber offers the free fish-cleaning service.

“It’s sad,” Burman said. “It wasn’t an easy decision for the board.”

The chamber operated the concession through a contract with Montana Fish, Wildlife & Parks. Burman said the contract is now open to any other nonprofit to bid on. Part of the problem the chamber had with the agreement is that money raised couldn’t go back into marketing the caviar.

She said the operation was also difficult since the chamber had no control over how many eggs might be retrieved in a fishing season, as well as keeping the eggs fresh once the fish were caught.

“Last year the crop was down, and we don’t see another big female crop (of fish) until 2032, because of how long it takes fish to mature,” Burman said.

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