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Pallid sturgeon

Pallid sturgeon, like this adult, are listed as an endangered species. The fish live in the lower Missouri and Yellowstone river drainages in Montana.

Endangered species like the pallid sturgeon, interior least tern and the Northern Great Plains piping plover will best be served by the U.S. Army Corps of Engineers adopting a management plan focusing on mechanical enhancement of the species’ habitats.

That’s the conclusion of the Corps following Brig. Gen. D. Peter Helmlinger’s Nov. 20 signing of a Record of Decision for the Missouri River Recovery Management Plan and Environmental Impact Statement. The document sets the course for how the agency plans to keep the three species alive from Fort Peck Dam in Montana downstream to the Missouri River’s confluence with the Mississippi River.

“Getting to this point reflects the tremendous efforts of a great team of partners and stakeholders who truly care about the future of the Missouri River,” Helmlinger said in a press release. “The amount of coordination required for something that involves such a cross-section of federal, state, local and tribal organizations can’t be understated.”

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Sturgeon embryo

A hatched embryo of a pallid sturgeon will drift for several days, requiring long stretches of free-flowing water. Dams and the reservoirs they create have been show to kill young sturgeon larvae.

Pallid sturgeon

As it relates to pallid sturgeon, the chosen alternative focuses on mechanical construction of spawning habitat and what’s called “interception and rearing complex,” or IRC, habitat by modifying and widening the river’s channel at “12 pair sites.” The work would take place on the lower river over seven years.

The plan is to create slower stretches of water, or modify existing portions of the river, to provide a place for the fishes’ larva to live. Beginning in 1945 the lower river was dredged to a depth of 9 feet and widened to 300 feet from Sioux City, Iowa, downstream to ease barge traffic.

Despite such habitat alteration, the reason for the pallid sturgeon’s decline has largely been attributed to the numerous dams built on the Missouri River. That’s because once pallid sturgeon larvae hatch, they drift downstream for seven to 11 days. After that the young fish need slower water and food to thrive.

On the upper Missouri, above and below Fort Peck Dam, the distance the larvae have to drift is believed to be too short. As a result, the young larvae end up at the head of Fort Peck or Sakakawea reservoirs where they die in sediment-laden waters too low in oxygen for them to survive.

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Intake Dam

Water flows over Intake Dam and into the Lower Yellowstone Irrigation Project outside Glendive. The dam is scheduled to be built higher and a channel cut to the right of the dam to allow native fish passage up and down the stream.

Yellowstone River

On the Yellowstone River, where pallid sturgeon also live, the Corps has committed to supporting the Bureau of Reclamation as it rebuilds Intake Dam and constructs a side channel meant to allow fish like pallid sturgeon the ability to swim around the dam and continue upstream — thereby possibly extending the distance that the fishes’ larvae has to drift. The dam construction was delayed after it was challenged in court by an environmental group, but a federal judge’s ruling in July green-lighted the project.

“Improvements to fish passage are expected to be a substantial step forward in assisting the long-term survival and recovery of the pallid sturgeon in the upper basin by providing access to up to 165 miles in upstream reaches of the Yellowstone River,” the EIS said.

The Corps plan includes no sampling of pallid sturgeon populations on the Yellowstone River, leaving that to the Bureau of Reclamation as part of its Intake Dam reconstruction. Instead, the Corps will focus minimally on fish in the Missouri River downstream of Fort Peck Dam, even though it has been demonstrated that the fish use both streams.

Although it will continue work on the Missouri below Fort Peck, the Corps EIS stated, “Meaningful levels of recruitment in this reach (below Fort Peck Dam) are improbable given the current constraints.”

Everything from “alteration of Fort Peck flows, temperature modifications at Fort Peck, and drawdown of Lake Sakakawea” are unlikely to result in pallid sturgeon larvae surviving in that stretch of the Missouri, the Corps concluded.

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Fort Peck Dam

The Fort Peck Dam on the Missouri River is located in northeastern Montana.

Downstream

Given that conclusion, the Corps has focused its recruitment efforts for pallid sturgeon much farther downstream. The agency plans to build and monitor three pallid sturgeon spawning sites on the lower river as part of its management plan.

The plan also could include “a one-time spawning cue test release for pallid sturgeon from Gavins Point Dam” if it’s determined during the first nine to 10 years of research that such a release of water is needed. Gavins Point Dam is on the Missouri River at the South Dakota-Nebraska border.

For piping plovers and least terns, the Corps has endorsed plans to “create (emergent sandbar) habitat through mechanical means at an average rate of 332 acres per year, in years where construction is needed, across the Garrison, Fort Randall, and Gavins Point reaches,” according to the Record of Decision.

Background

The pallid sturgeon was listed as endangered in 1990. The fish’s lineage dates back to the era of the dinosaurs. Fossilized pallid sturgeon have been dated to 78 million years ago. The slender, shovel-snouted fish are bottom feeders that closely resemble the more common shovelnose sturgeon. The pallid sturgeon of the upper Missouri tend to live longer and grow larger — up to 6 feet long.

It was estimated in the 1990s that only 125 wild adult pallid sturgeon still existed in the Missouri and Yellowstone Rivers above Lake Sakakawea to Fort Peck Dam. The population above Fort Peck Reservoir on the Missouri is estimated at less than 45 adults. Hatchery-reared sturgeon, raised from eggs taken from native fish, have been released in the Yellowstone and Missouri rivers to beef up the existing populations.

The Corps justified its Record of Decision by noting that the agency and the U.S. Fish and Wildlife Service have worked with stakeholders for more than five years to find an alternative that would help the sturgeon, tern and plover while also minimizing “impacts to stakeholders.”

The Record of Decision is available online at: https://www.nwo.usace.army.mil/mrrp/mgmt-plan/ in the “Final Documents” section.

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