RIVERDALE - They are survivors from prehistoric times, real river monsters, but few remain.
The number of adult pallid sturgeon that make the journey each spring through the confluence area of the Missouri and Yellowstone rivers is estimated at 150 to 200, but no one knows for sure. Pallid numbers are so few that a single disastrous event could prove catastrophic to their survival.
The rivers that give them life have been so altered by man that the survival of the species was very questionable a few short years ago. Pallids were in such dire straits that they were placed on the endangered species list. The U.S. Fish and Wildlife Service began a pallid sturgeon recovery program in the early 1990s. The Garrison Dam National Fish Hatchery has played a leading role from the outset.
Article Photos
Kim Fundingsland/MDN
Pallid sturgeon have very small eyes, pointed nose and a bony appearance. They are ideally suited for traversing and surviving in murky river water.
One of the first issues was to determine how many pallids existed, and where they were located. Biologists knew they'd have to trap adult pallids so that they could collect eggs, but it was like searching for the proverbial needle in a haystack. Eventually biologists were able to establish a pattern used by the ancient pallids. The knowledge has led to a capture process that has proven vital to the possible recovery of the species.
It is work unlike any other associated with most species of fish during the spawn. There are so few remaining pallids in the Upper Missouri and Yellowstone rivers that catching one or two is a considerable achievement. Sometimes there are surprises, such as one pallid captured in the confluence region recently.
"It was a 50-pounder and we'd never seen her before. It was amazing," said Rob Holm, project leader. "Another fish we caught we hadn't seen for 20 years."
The "new" pallid will receive a small chip that will be inserted under her skin. The chip, which will contain the fish's known history, can be read by a hand-held scanner. The other pallid referred to by Holm carried an old tag that led to its identification. The two pallids were among four initially captured by biologists working the murky waters of the confluence area. All were transferred to a large holding tank at the Garrison Hatchery.
"The two bigger fish are in the 50-pound range. One old male is 35 pounds and the other 43," said Holm. "They are natural fish, all probably 60 years old at least."
Biologists hope to capture a few more pallids to bolster this year's artificial spawning effort. Genetic diversity is considered important to the future of the species. It is documented that some pallids are better producers of young than others but, with so few to choose from, biologists cannot always promote new families of pallids.
Another surprise among the pallids already at the hatchery is one whose head had become stuck in a rubber gasket, debris that found its way into the river with near fatal results. The pallid was last captured in 2000.
"It had that gasket around its head," said Holm. "It was emaciated. We thought that fish was a guy initially, but it's a girl and we will be spawning her."
The fish was a good find for biologists. Another good find this year was a fish Holm described as a "frequent flyer."
"We caught him in 2001 and again in 2002, several times actually," said Holm. "He had scoliosis and we thought he was going to die."
The pallid has an upturned tail that easily distinguishes it from others in the holding tank. It is a true survivor that may play an important role in the survival of the species.
"These fish will stay on the endangered list until they can recruit on their own," said Holm. "We've been working on this since 1993 and we're not seeing new fish. We suspect some pallids are hanging out in Lake Sakakawea."
Sightings of sturgeon, likely pallids, have been reported in Lake Sakakawea but their numbers and whereabouts remains undetermined. The reservoir could be home for pallids that have been raised in the hatchery and released back into the wild.
"Some fish just disappear. They have transmitters. You'd think you'd run into them," said Holm. "Pallids have been caught in smelt nets near Four Bears."
Pallids don't reach breeding age until 10-14 years old. That means recovery is a very slow process. If the hatchery-reared pallids don't begin to replace the aging river monsters, the older fish will eventually die off, taking with them millions of years of evolution.