UNION, Neb. — Backhoes are breaking into the earth along the Missouri River in an attempt to re-create inviting habitats for big, strange-looking fish that have sparked debate and lawsuits for more than a decade.

With its ridged back, long tail and beady eyes, the pallid sturgeon looks like a holdover from the age of the dinosaurs. But it is now struggling to survive.

Up and down the Missouri River, the Army Corps of Engineers is digging into and removing sets of dikes jutting out into its waters to comply with the federal Endangered Species Act. And by July 1, the corps plans to create 1,200 acres of new habitat for the pallid sturgeon.

Three years ago, U.S. Fish and Wildlife Service biologists ordered the corps to regulate the flow of the river to mimic its original seasonal rise and fall. But in December they backed off that order and told the corps that summer water levels could be kept high enough to continue barge shipping — if the habitat was created.

Stocks of farm-raised sturgeon will be used to replenish populations throughout the river system in the hope that they will reproduce naturally, said Mark Drobish, a fishery biologist with the corps.

‘‘If they're doing it on their own, I think the service and .... pretty much any biologist would agree that that's recovery of the species,'' Drobish said.

In 1990, the sturgeon was placed on the federal endangered-species list.

Pointing across a 600-foot-wide section of the river near Union, Remus said the corps intended to convert about half of the width into habitat.

The navigation channel used by shipping barges along the river is about 300 feet wide and 9 feet deep, Remus said.

‘‘What we're trying to do is utilize that extra 300 feet,'' Remus said.

The Corps, the U.S. Fish and Wildlife Service and state agencies will be monitoring the success of the projects, Drobish said.

But because the pallid sturgeon matures so slowly — females can reach 15 years old before sexual maturity — it may take 40 years before the species recovers, Drobish said.

The Corps' plans for the river have drawn fire from both conservationists and shipping businesses.

New drought conservation measures will limit water releases upstream — this year cutting the shipping season on the lower Missouri by 33 days.

And uncertainty over the future of shipping on the river during the 14-year battle between conservationists and other interests has cut into the shipping industry.

No barges this year are shipping north of Nebraska City, which is about 54 miles south of Omaha, said Kevin Knepper, general manager of the Big Soo Terminal in Sioux City, Iowa.

Knepper said he was glad to see habitat reintroduced on the river but said the potential of conservationists filing lawsuits against the corps to stop barge traffic has made shipping companies avoid using the Missouri River, Knepper said.

MEMCO Barge Line in Chesterfield, Mo., did not make any contracts this year to work that part of the Missouri River, said Mark Carr, a company spokesman.

‘‘It's just uncertainty of what the river conditions would be,'' Carr said, noting that the multiyear drought in the region was also a factor.

‘‘We need the system to be reliable,'' Knepper said.

The corps' conservation efforts on the river are a step in the right direction, said Vince Shay, state director of the Nature Conservancy.

‘‘Anything that's beneficial to the sturgeon or any of the at-risk species in the river is a good thing. ... But it's just a little thing,'' Shay said.