FAMILY: Acipenseridae

DESCRIPTION: the snout is flattened and shovel shaped with a protrusible underslung mouth.  There are four barbels located a third of the way between the mouth and snout, with the inner barbels often slightly anterior to and shorter than the outer barbels.  There are five rows of bony scutes running the length of the fish.  The tail region (caudal peduncle) is long and thin, and is covered completely by the body scutes.  Overall color is a pale grayish white.  Pallid sturgeon can reach a maximum length of about 60 inches and a maximum weight of about 86 pounds in the northern part of their range, though fish from southern locations are smaller.

STATUS: Listed as a Federally endangered species on September 6, 1990 (Federal Register 55:36641-36647) over its entire range.

REASONS FOR CURRENT STATUS:  Populations have undergone severe decline due to habitat modifications, commercial fishing, and possibly pollution.  Dams block migration, fragment the population, and alter flow rates and temperature regimes required by the species.  Channelization reduces habitat diversity characterized by side channels, chutes, sloughs, and floodplains.  Early commercial harvest is thought to have greatly reduced the population prior to construction of dams on the Missouri River.  Large scale inflow of pollutants from many sources over the length of the species' range may also negatively affect reproduction.

REPRODUCTION AND DEVELOPMENT:  Lengthy maturation.  Males mature sexually at 7-9 years, females mature at 7-20 years.  Individuals may require several years between spawns; males are thought to spawn at 2 to 3 year intervals, females at 3 to 10 year intervals.  Spawning habitat is unknown, but its suspected to involve rock or gravel substrates in main river channels, and warming water in late spring or early summer is thought to be a spawning trigger.  Development includes a planktonic larval stage.  Growth is rapid during the first four years, then slows to approximately four inches per year for the next five years.

RANGE:  Historically found in the lower 200 miles of the Yellowstone River; the Missouri River from Fort Benton, Montana to St. Louis, Missouri; the Mississippi River from St. Louis to its mouth; the lower reaches of larger tributaries such as the Platte, Kansas, St. Francis, Ohio, Arkansas, and Yazoo/Big Sunflower Rivers; and the Atchafalaya River.  Currently found in fragmented segments of free flowing river within historic range, as well as upstream portions of impoundments.

POPULATION LEVEL:  Exceedingly rare.  Population is thought t have declined precipitously over the past century.  Over its entire range, the species was sighted an average of 50 times per year in the 1960's, but just seven times per year in the 1980's.

HABITAT:  The species requires turbid water, diverse habitat types, and flow rates afforded by large, free flowing rivers.

MANAGEMENT AND PROTECTION: Known populations consist entirely of adult fish.  Spawning may be occurring, but recruitment is suspected to be nonexistent.  There are very few records of larval or juvenile pallid sturgeon being found in the wild.  Stocking of captive reared individuals is being done to ensure survival of the species while habitat restoration efforts are ongoing.

Species recovery plan calls for habitat restoration and captive propagation to establish self-sustaining population segments within the historical range by 2040.  This will entail reconnecting some river features cut off from the Missouri and Mississippi Rivers and partial restoration of high water flows through dam release.  Restoration of woody debris in native rivers may help the recovery effort.

The states in which pallid sturgeon live have adopted a variety of fisheries regulations to protect individuals of the species.  North Dakota, South Dakota, and Louisiana require live release of all sturgeon, Montana and Kansas do not allow commercial harvest of sturgeon.  Given the long time to maturity and intervals between spawns, loss of any individual is detrimental.

Information summarized from:

US Fish and Wildlife Service.  1993.  Pallid sturgeon recovery plan (9.65 MB).  USFWS, Denver, Colorado.  55 pp.

Additional information available at:

NatureServe Explorer: An online encyclopedia of life [web application]. 2001. Version 1.6. Arlington, Virginia, USA: NatureServe. Available: http://www.natureserve.org/explorer. (Accessed: August 15, 2002).

United States Fish and Wildlife Service. 1990. Endangered and threatened wildlife and plants: determination of Endangered status for the pallid sturgeon. Federal Register 55:36641-36647.