The pallid sturgeon was not described as a species until 1905, and remains one of the least known of the large, freshwater fishes. The original distribution of pallid sturgeon was probably in the Yellowstone River from the confluence of the Bighorn River downstream to the confluence with the Missouri River; in the Missouri River from Great Falls, Montana; downstream to the confluence with the Mississippi River; and in the Mississippi River from the confluence with the Missouri River to the Gulf of Mexico. The one or two early records of pallid sturgeon from the Mississippi River above the confluence of the Missouri River are likely the result of strays because, prior to construction of navigational features, the upper Mississippi River probably did not provide the preferred turbidity and temperature range of the species (National Paddlefish and Sturgeon Steering Committee 1992).
The pallid sturgeon (Scaphirhynchus
platorynchus) was listed as an endangered species on September 6, 1990 in accordance with
provisions of the Endangered Species Act of 1973, as amended (National Paddlefish and
Sturgeon Steering Committee 1992). In the early 1900's, pallid sturgeon were reported to
comprise only 1 in 500 of river sturgeon captured in the Mississippi River at Grafton,
Illinois. However, since the development of dams and reservoirs on the Missouri River, the
species has declined even further. There are now only remnant, populations of pallid
sturgeon remaining in each of the reservoir complexes in the Dakotas and remaining
riverine habitat, the impounded waters apparently do not meet the requirements of the
species because successful reproduction has never been documented. It is also likely that
the forage base once used by pallid sturgeon has been greatly altered, thus affecting
growth and reproduction. The largest remaining populations of pallid sturgeon appear to be
in the upper Missouri River above Ft. Peck Reservoir in Montana, in the Missouri and
Yellowstone rivers above Garrison Reservoir in North Dakota and Montana, respectively, and
in the Mississippi River below St. Louis, Missouri and in Louisiana near the Old River
Control Structure. It is doubtful that any natural reproduction has occurred during the
last decade (National Paddlefish and Sturgeon Steering Committee 1992).
Because pallid sturgeon are so rare, little is known about their life requirements. They are known to prefer large, turbid, free-flowing river habitat with rocky substrate. Pallid sturgeon are well adapted to life on the bottom and inhabit areas of swifter water than do the smaller shovelnose sturgeon. The primary forage base for adult pallid sturgeon prior to extensive modifications of riverine habitat is assumed to have been flathead chubs, plains minnows, and western silvery minnows found in association with sand and gravel bars. The few pallid sturgeon in captivity are fed goldfish, crayfish, and minnows (National Paddlefish and Sturgeon Steering Committee 1992).
During the summer of 1999 Jim Milligan and his staff of the U.S. Fish
& Wildlife Service, Fisheries Resources 
Office
in Columbia, MO collected the first known wild larval pallid sturgeon from the
lower Missouri River. The young sturgeon (photo at left) was
collected in a restored side ch
annel
(or habitat bead) of the Lisbon
Bottoms Unit (photo at right) of the Big Muddy National Fish and Wildlife
Refuge. This finding gives biologists hope that their efforts to restore
side channels and floodplain habitats along the lower Missouri River are
successfully creating habitats essential to the continued existence of this
ancient species. It is not known where the young sturgeon was spawned
(undoubtedly miles upstream), but it is known that the shallow off-channel
habitats provided by the Lisbon Bottoms chute were being used by the young
sturgeon as a refuge from the swift main channel currents.
Pallid sturgeon are known to hybridize with the smaller shovelnose sturgeon. In the lower Mississippi River in Missouri, hybrids are more common than pallid sturgeon. Hybrids were first identified in the Mississippi River below St. Louis, Missouri, in the late 1970's, and most recently in Louisiana near the Old River Control Structure. These hybrids may constitute a serious threat to the survival of pallid sturgeon in the southern portion of their range because of competition and the potential for genetic swamping (National Paddlefish and Sturgeon Steering Committee 1992).
Pallid sturgeon were first artificially spawned in Missouri in 1992. A number of Federal and State hatcheries are conducting studies that will benefit management of this species, including improved spawning techniques to insure survival of broodstock and production of viable eggs and fry, and the identification of foods and feeding techniques that improve growth and survival of fingerling and adult fish (National Paddlefish and Sturgeon Steering Committee 1992).
Reference: National Paddlefish and Sturgeon Steering Committee. 1992. Framework for the Management of Conservation of Paddlefish and Sturgeon Species in the United States. U.S. Fish and Wildlife Service, Washington, D.C. 12 pp. + App.