With a "no-vacancy" sign hanging on the adult pallid sturgeon tanks at Garrison Dam National Fish Hatchery, hatchery manager Rob Holm grows more optimistic about stalling the looming extinction of the endangered, prehistoric fish.

Twenty-four adult pallids, including two females, are in temporary residence at the hatchery in Riverdale after the latest pallid-collecting expedition in the upper Missouri River.

"That's a few more than we ever have had," Holm said by telephone Wednesday. "I just went by them all. They look pretty happy out there."

Holm is hoping to collect a "couple hundred thousand" eggs from each female when they are spawned about mid-June. Although each female weighs in the 50-pound range, the number of eggs they produce depends on Mother Nature and the fish.

The goal is to raise up to 35,000 5-inch pallids that would be tagged and released back into the river this fall. Another 6,300 to 6,400 young pallids would be kept in the hatchery until spring when they grow to about 10 inches before being tagged and released.

With those reservations made, any excess young pallids would be shipped out as fry and stocked in the Missouri and Yellowstone rivers, Holm added.

The Garrison Dam hatchery is working with hatcheries in Miles City, Mont., and Gavins Point, near Yankton, S.D., to ensure they obtain the best genetics from the captured adults. Those hatcheries also have pallid sturgeon on hand for spawning.

Scientists estimate that fewer than 200 spawning-age pallids are living in the river between Montana's Fort Peck Reservior and Lake Sakakawea. And many of those fish, which probably were spawned before the Missouri River was dammed, are either near or fast approaching the end of their lives.

Although 22 males are far more than the hatchery needs for spawning, the milch of the other males won't go to waste.

"We want to conserve as much of the gene pool as possible. It was the last week out there, and we had space for 24. So we would keep all the males and preserve milch from all the males so that if the fish do die before we collect them again, we have their milch," Holm explained.

That's one of the reasons he's optimistic about pallid sturgeons' survival.

"We're learning more and more," he said as the sound of his knuckles knocking on wood could be heard in the background.

About 110 hatchery-raised pallids had been recaptured as of last fall, Holm said.

"With the spring monitoring, we should be getting more information," he said, adding that more researchers will be out looking for pallids when U.S. Army Corps of Engineers researchers join U.S. Fish and Wildlife Service researchers on the water.

More pallids stocked in 2002 have been recaptured, probably because they are the biggest.

"We also collected five that were stocked as larva," Holm said. "All sizes are surviving."

Eight-inch pallids stocked in Missouri 2½ years ago have grown to more than 2 feet long. "They appear to be finding food and growing well," Holm added.

Other pallids have shown significant movement.

"Some fish have traveled 250 to 350 miles from where they were stocked to where they were collected," Holm explained. "They obviously are out there moving around, finding good habitat, good food and growing. Those are all good indicators that our stocking effort will keep (pallids) around for a while."

(Reach outdoor writer Richard Hinton at 701-250-8256 or richard.hinton@;bismarcktribune.com.)