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Fish on the line

Pallid sturgeon persevered for 70 million years. Why are they struggling now in Montana?

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From the beginning, the U.S. Army Corps of Engineers’ dramatic makeover of the river seemed the obvious culprit for the species’ decline. Pallid sturgeon evolved in warm, dynamic rivers that were free to jump their banks and ramble about the floodplain, muddying themselves with the dirt and clay churned up in the roil. Flows swelled every spring with snowmelt, peaked again with early summer rains, then dropped off in early fall. This ebb and flow added organic matter and nutrients to the river and redistributed sediment. For native fish, these changes—and their associated shifts in temperature and turbidity—triggered spawning migrations, and enhanced spawning conditions and nursery habitat.

Today’s “Big Muddy”—a nickname the Missouri shares with its cousin, the Mississippi—is not nearly as big or muddy as it once was. At the start of the 20th century, the Corps began wrestling the river into submission, hoping to create jobs, minimize flood risk and ensure a reliable thoroughfare for the barge industry. Six dam and reservoir projects went up in the Upper Basin, and the river’s southern stretches were straightened and stabilized.

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  • Photo by Aaron Delonay

The dam system, which provides water for cities, irrigation, hydropower and recreation, was one of the 20th century’s great engineering achievements. But it wreaked ecological havoc, severely altering the river’s natural temperature and hydrologic patterns, which play key roles in the movement, growth and reproduction of native fish. It’s halted most annual floods, preventing the river from connecting to low-lying lands and reducing key nutrients, forage and habitat for young fish.

Though hard data are lacking (pallids weren’t recognized as a separate species from the smaller, darker shovelnose sturgeon until 1905), records suggest pallids may never have been common. Still, according to Braaten’s calculations, roughly 1,000 cruised the river between Fort Peck Dam, in eastern Montana, and North Dakota’s Garrison Dam when the latter was finished in the early ’50s. Fewer than 150 wild fish persist here today.

The U.S. Fish and Wildlife Service listed pallid sturgeon as endangered in 1990 in response to declines throughout its range, which runs from Montana to the Louisiana Gulf—some 3,000 total river miles. It’s considered an indicator species for the Missouri; if it’s in trouble, other species probably are, too. Indeed, two native birds—the piping plover and least tern—are listed under the Endangered Species Act, due in part to the loss of winter and midstream nesting habitat. And roughly half of the river’s 106 native fish species are uncommon, rare or decreasing across all or part of their ranges.

In today’s Missouri, the pallid sturgeon’s biological quirks aren’t doing it any favors, either. Pallids are poky and particular about life and love. They grow slowly, live for decades, don’t reach sexual maturity until they are at least 10 years old and spawn only every few years. And if the spawning set-up isn’t perfect—if the river is too cold, for instance—the females re-absorb their eggs and wait for conditions to improve.

In the upper river, the dam-locked run where we found Code 117 has been a top priority for recovery teams because it hosts the largest remaining cadre of “heritage” fish, the biggest (50-70 pound), oldest (40- 80-year-old) wild fish that hold the genetic key to their species’ long-term survival. Scientists believe the Upper Missouri adults are genetically distinct from their Lower Missouri and Mississippi River counterparts, where hybridization with shovelnose sturgeon is thought to be more common.

The first 10 years of pallid recovery here focused on preserving these genes and stocking the river with hatchery fish. “(Stocking) has certainly helped boost population numbers,” says George Jordan, who coordinates recovery for the Fish and Wildlife Service. “(But) if we stopped stocking now, pallids won't be any better off.” For pallids to make it, they must spawn and their babies must survive.

In 2000, the Corps tapped Dave Fuller and Pat Braaten to lead an experimental effort to help that agency comply with the Endangered Species Act and boost the species’ prospects in the upper river. Scientists have long suspected that channelization and bank stabilization on the Lower Missouri, and dams and reservoirs on the Upper Missouri, were responsible for the species’ decline. But the details—the exact whys and hows—were still uncertain.

Braaten had been working downstream in Missouri and Kansas on another native fish study. He grew up fishing in Minnesota and by high school knew that he wanted to be a fisheries biologist. His mother remembers him cutting open his catches to see what the fish were eating. “Now, I get paid to do that,” he chuckles.

Fuller’s road to fisheries work was less direct. He started out in engineering, following in his father’s footsteps. But the idea of working with fish lingered, and in the early ’90s, he moved from New York to Bozeman, chasing dreams of blue-ribbon trout streams. “I told my folks the move was for school, but it was for fishing,” he confesses. After taking a year off to do Westslope cutthroat trout habitat work, he decided to switch careers and eventually ended up in Fort Peck, studying sturgeon, catfish, suckers and chubs.

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  • Photo courtesy of USGS

The two biologists soon discovered they had much in common. “We hit it off really well,” Braaten says. Both in their early 40s, they dress alike—T-shirt, ball cap, jeans, boots—share a love for bird-hunting and the outdoors, and even speak in the same cadence, their voices equal parts dirt and drawl. But it’s their differences that make them a good team: “I’m more the thinker, the idea man,” says Braaten. Fuller is “extremely good at making things happen in the field.”

The Corps’ plan when the two teamed up at Fort Peck was to help restore key aspects of the river’s ecology that had been lost to dams, and see how the fish responded. The Fish and Wildlife Service, which drafts the biological opinion telling the Corps what recovery measures to implement, recognized that the fundamental aspect of all rivers is the seasonality of flow. If sturgeon did well before people altered things, then adjusting the dams’ releases to better mimic natural conditions would, in theory, enhance spawning and juvenile development for pallid sturgeon and other native fish species.

They suspected that water temperature might be limiting reproduction and the survival of hatchlings. At Fort Peck, the dam releases water from the reservoir’s chilly bottom, making the river much colder than it would be naturally. The Fort Peck Flow Modification Project, or “Flow Mod,” would address this with two test releases of warm surface water over the spillway in 2001 and 2002, followed by spills once every three years if reservoir levels allowed.

At the time, this sort of thinking was taking hold on dammed rivers worldwide. In the 1990s, says Brian Richter, a freshwater conservation expert with The Nature Conservancy, scientists learned a lot about how important natural fluctuations were in maintaining river systems and native species. In the last decade or so, this knowledge has begun to influence management, with numerous experiments under way to “renaturalize” rivers without removing dams. But there are plenty of obstacles: funding, politics, the limitations of existing infrastructure—and on the Missouri, nature itself.

As it turned out, Flow Mod was not so much born as stillborn. Low water levels in the reservoir behind the dam prevented the Corps from conducting test spills in 2001, 2002 and 2003. The region was suffering from severe drought, making it technically impossible to spill since the reservoir was 30 to 50 feet below the spillway.

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