RIVERDALE - A series of reservoirs on the Missouri River has changed habitat vital to the growth and development of several varieties of fish. Shovelnose sturgeon, and the closely related and larger pallid sturgeon, are two fish that have struggled to survive against changing habitat.
The problem for pallids became so severe that the bottom-dwelling fish was placed on the endangered species list in 1990. In response, the U.S. Fish and Wildlife Service launched a pallid sturgeon recovery program in which the Garrison Dam National Fish Hatchery has played a major role. It is there that pallids captured in the wild have been artificially spawned and the young returned to the Missouri and Yellowstone Rivers.
Although the pallid remains on the endangered species list, thousands of young pallids released into the wild have greatly enhanced the odds of the survival of the rare fish. Now there is growing concern over another sturgeon - the more common shovelnose. Again the Garrison Hatchery is playing an important role in the future of a unique fish.
The tanks in this isolation room at the Garrison Dam National Fish contain more than 2,000 shovelnose sturgeon. Isolation is necessary to prevent any possible transfer of disease within the hatchery’s Sturgeon Building.
It is easy to see how “shovelnose” sturgeon get their name. This young, 8-inch sturgeon will soon be released in Wyoming.
"We have a total of 2,177 in the isolation room," said Carmen Sheldon, biological technician, Garrison Dam National Fish Hatchery. "They are under quarantine, so we keep the pallid sturgeon and the shovelnose separate."
Isolation is a necessary precaution to prevent any transfer of disease between the two closely related fishes. The doormat leading into the isolation room is coated with disinfectant, a further precaution against unwanted disease entering the room and possibly reaching the young shovelnose sturgeon inside. Shovelnose are known carriers of a disease that can be transferred to pallids. If the shovelnose should become infected and released into the wild where they interact with pallids, the result could greatly hamper the pallid recovery effort.
"We provided the isolation room to raise a pile of shovelnose this year," said Rob Holm, project leader. "They have to be specific to the drainage from where they came in Wyoming and Montana. They want to maintain the genetic integrity of the fish being stocked."
Shovelnose sturgeon are not an endangered species. Rather their status is considered "vulnerable." That means shovelnose could become a candidate for endangered status without any positive changes to reverse their decline. In North Dakota, fishermen who hook and land sturgeon must release the fish immediately.
"Shovelnose numbers where habitat hasn't been altered are OK," said Holm. "Shovelnose numbers where you've got habitat issues aren't so hot."
Like many fish, shovelnose sturgeon move upstream in early spring to spawn. Primary spawning habitats include the upper reaches of tributaries flowing into the Yellowstone and Missouri rivers. Shovelnose larvae float downsteam as far as 150 miles. However, their growth has been varied since the reservoirs were constructed on the Missouri River.
"Above Fort Peck, where things haven't changed much, you are talking about shovelnose reaching maybe 10 to 15 pounds," explained Holm. "When you get down here in a managed, channelized river, you are talking about 3-pound fish. Here they might be 5 or 50 years old and they are the same weight. They hit a plateau and that's it."
Closely related pallid sturgeon can vary in weight too depending on where they live. In the Mississippi River in Louisiana, considered the southern range of the species, a fully grown pallid might reach 15 pounds.
"You don't see 30-, 40- or 50-pound pallids like you do here," said Holm.
The shovelnose at the Garrison Dam Hatchery are due to be released in Wyoming and Montana in the second week of October. Their average length is about 8 inches. Although hatched at the same time and from the same shipment of eggs, some are noticeably smaller. All will have to make the adjustment from hatchery holding tanks to natural habitat in order to survive and increase the shovelnose population in drainages where they have lived for thousands of years.