Pallid Sturgeon - Scaphirhynchus albus
The pallid sturgeon is the larger of the two species of sturgeon found east of the Continental Divide. It grows to about 60 pounds. Because it is rare and we know so little about it, the pallid sturgeon is a Montana Fish of Special Concern and is also on the Federal Endangered Species List. This fish is the subject of an ongoing research project (FWP).
The pallid sturgeon is a large fish (to 186 centimeters) with a heterocercal tail, a long slender caudal peduncle, a flat shovel-shaped snout, four fringed barbels on the snout, a ventral mouth, and large bony scutes on the head, back, and sides; 37 to 43 dorsal rays; 24 to 28 anal rays (Page and Burr 1991). The pallid sturgeon is similar to the shovelnose sturgeon but has no scale-like scutes on the belly, the bases of the outer barbels usually are posterior to the bases of the inner barbels, the inner barbels are shorter, the head is larger, the mouth is wider, the eye is smaller, and the color is usually paler (gray-white above and on sides) (Page and Burr 1991).
Summary of Observations Submitted for Montana
Number of Observations:
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Pallid sturgeon use the lower Yellowstone River primarily during spring and summer, but during fall and winter use the Missouri River below the confluence with the Yellowstone (Tews 1994, Bramblett 1996). Some pallid sturgeon use the Fort Pack tailrace yearlong, but others move downstream in spring (in one case more than 300 kilometers) (Tews 1994).
Pallid sturgeon use large, turbid rivers over sand and gravel bottoms, usually in strong current; also impoundments of these rivers (FWP). In Montana, pallid sturgeon use large turbid streams including the Missouri and Yellowstone rivers (Brown 1971, Flath 1981). They use all channel types, primarily straight reaches with islands (Bramblett 1996). They primarily use areas with substrates containing sand (especially bottom sand dune formations) and fines (93% of observations) (Bramblett 1996). Stream bottom velocities ranged between 0.0 and 1.37 meters per second, with an average of 0.65 meter per second (Bramblett 1996). Depths used were 0.6 to 14.5 meters and averaged 3.30 meters, and they appeared to move deeper during the day (Bramblett 1996). Channel widths from 110 to 1100 meters are used and average 324 meters (Bramblett 1996). Water temperatures used ranged from 2.8 to 20 degrees C. (Tews 1994, Bramblett 1996). Water turbidity ranged from 12 to 6400 NTU (Turbidity Units) (Tews 1994).
Aquatic insects and minnows have been found in the stomachs of pallid sturgeon (Brown 1971).
Annual home ranges for pallid sturgeon in Montana ranged from 12.4 to 331.2 kilometers with a median of 52 kilometers; seasonal home ranges were smaller in fall and winter than in spring and summer (Bramblett 1996). Sturgeon were found to have moved 54% of the time between relocations; they moved up to 21.4 kilometers per day and 9.5 kilometers per hour (Bramblett 1996). Adult females are generally larger than males.
Adult pallid sturgeon populations in Montana display a skewed size structure comprised of only large (old-age) fish (AFS website 2003).
Once pallid sturgeon spawn the resulting larvae have a strong tendency to drift great distances downstream over a long period of time (Kynard 1998). This behavior is thought to be one of the limiting factors affecting larval survival. It has been suggested that larval pallid sturgeon may end up being deposited in downstream reservoirs and consequently never reach suitable rearing habitat. Pallid sturgeon are long-lived and are thought to spawn at several year intervals. Females may not reach sexual maturity until they are 15 to 20 years old (Dryer and Sandvol 1993). Because of unique biological characteristics, including obligatory lengthy migrations and larval drift distances, high habitat specificity and late sexual maturity, pallid sturgeon is a species vulnerable to extirpation (AFS website 2003).
Beginning in 1996, research efforts focused on pallid sturgeon recovery and preserving the pallid sturgeon genetic pool through stocking. The main purpose of the stocking program is to preserve the genetic pool and reconstruct an optimal population size within the habitat's carrying capacity (Krentz 1997a) (AFS website 2003).
One of the most obvious detrimental changes in the pallid sturgeon environment was the damming of the Missouri River and several other important tributaries. Efforts are now being directed at restoring the river to a more normal condition. In 2000, the U.S. Fish and Wildlife Service (USFWS) completed an Endangered Species Act consultation with the U.S. Army Corps of Engineers regarding operation of Missouri River dams. Through an informal agreement the U.S. Bureau of Reclamation (BOR) has agreed to provide a dominant discharge spring pulse out of Tiber Reservoir every 4 to 5 years for Missouri River fish migrations which could help the Upper Missouri River pallid sturgeon population. To address pallid sturgeon passage and entrainment on the Yellowstone River, the USFWS has begun consultation with BOR regarding problems at Intake Diversion Dam. The future for pallid sturgeon recovery may continue to be uncertain even after positive changes have been implemented because pallid sturgeon populations are so depleted and the newly stocked fish will take at least 15 years before the females first reach sexual maturity and begin to spawn. Therefore, it is important to realize that immediate evaluations are impractical and recovery will take a dedicated, long-term commitment (AFS website 2003).
Implementing the pallid sturgeon recovery program in this area is a multi-state and agency task. To facilitate this, the Montana/Dakota Pallid Sturgeon workgroup was organized in 1993. The group is comprised of representatives from MFWP, NDGF, USFWS, USBOR, WAPA and PPL-MT, and acts in an advisory role identifying research needs and funding sources, developing workplans and providing an opportunity for communication between biologists and agency personnel (AFS website 2003).
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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- Albers, Mark., 1995, Draft Biological Assessment: Tongue River Basin Project. May 1995. In Tongue River Basin Project Draft Environmental Impact Statement. Appendix B. June 1995
- American Fisheries Society (AFS), Montana Chapter Website.
- Additional Sources of Information Related to "Fish"