The pallid sturgeon (Scaphirhyncus albus) is one of the rarest and largest freshwater fish in North America. It and the smaller, more common shovelnose sturgeon (Scaphirhyncus platorhynchus), are the only sturgeon species native to the Missouri and Yellowstone rivers in Montana. Pallid sturgeons live to be older than 50 years and can reach lengths of over 6 feet and weigh over 75 pounds.
The pallid sturgeon is a Montana Species of Concern and was classified as "endangered" by the U.S. Fish and Wildlife Service in 1990. Its historic range included the middle and lower Mississippi River, the Missouri River, and lower reaches of the Platte, Kansas, and Yellowstone rivers. In Montana, pallids have been found in the Missouri River between the mouth of the Marias River and Fort Peck Reservoir; between Fort Peck Dam and the North Dakota border; and in the 70 miles of the Yellowstone River below the mouth of the Powder River. Their preferred habitat is the bottom of large, turbid, relatively warm, free-flowing rivers.
Man's alteration of large river systems is believed to be the primary cause of the pallid sturgeon's decline. Damming, channelizing, and diking has destroyed much of the natural function of the river, destroying or inundating spawning and rearing habitats; reducing the deposition of woody debris, organic material, and inorganic sediments; disrupting natural flow and temperature regimes; and lowering the turbidity preferred by pallid sturgeon. As a result, overall habitat diversity, productivity and availability have been severely impaired.
Although some spawning has been documented with the discovery of a few pallid sturgeon fry, no recruitment has been documented for at least 30 years. After hatching, pallid sturgeon fry drift in the river for several days before settling out of the water column. It is believed that pallid sturgeon fry are drifting into the unsuitable habitats in the upper reaches of Fort Peck Reservoir and Lake Sakakawea, where they die. Without recruitment, the two pallid sturgeon populations in Montana, in the Missouri river above Fort Peck Reservoir and in the lower Yellowstone River and Missouri River below Fort Peck Dam, are comprised of old fish and are estimated to contain fewer than 30 and 200 adults respectively. These wild populations are expected to go extinct by 2018.
Recovery of the endangered pallid sturgeon as a self-sustaining population will require restoration of the river flows, temperatures, turbidity and habitats. Since 1994, artificial propagation has been used to maintain the pallid sturgeon populations in Montana until the needed improvements to habitat and river function can be made. Each year, a few of the remaining wild adult pallid sturgeon are captured, spawned and released. The fertilized eggs are hatched and the resultant fish are reared in state and federal hatcheries until they are large enough to stock. Some of these hatchery fish are also incorporated into the pallid sturgeon broodstock at Gavins Point National Fish Hatchery. This broodstock will serve as a source of genetically pure fertilized pallid sturgeon eggs after the existing wild adult populations go extinct. Female pallid sturgeon do not become sexually mature until they are approximately 15 years old, so it remains to be seen whether the hat hery program will successfully achieve its goal of restoring the pallid sturgeon in Montana.
Recovery of the magnificent pallid sturgeon will require changes in the way dams and water are managed in the Missouri and Yellowstone rivers. Just as bighorn sheep, mountain goats, mule deer, elk and antelope are part of what makes Montana the "last best place", pallid sturgeon too are part of Montana's wildlife legacy.