Funding Program:  Fisheries: Aquatic and Endangered Resources

Statement of Problem: The life history, behavior, and habitat requirements of the endangered pallid sturgeon are poorly understood. This paucity of critical data for this species has limited the ability of management agencies to recover the species. Evidence suggests that recruitment of pallid sturgeon to the adult population is limited or non-existent in the Missouri River though the closely-related shovelnose sturgeon is reproducing and recruiting. The decline in the pallid sturgeon may be due in part to poor reproductive success. The specifics of the reproductive physiology and spawning behavior of both species are poorly documented. 

Numerous factors may play a role in limiting spawning activity and reproductive success for sturgeon. These may include hydrology, temperature, impediments to migration, lack of spawning substrate, inadequate numbers of reproductive adults, hybridization with closely related sympatric species, predation and contaminants. Recent evidence suggests that some reproduction and recruitment may be occurring in the Lower Missouri River and in the Mississippi River. Larval pallid sturgeons were identified from samples collected in these locales in 1998, 1999 and 2000. Preliminary evidence also suggests that pallid sturgeon are successfully spawning below Fort Peck Dam in the Upper Missouri River, though recruitment apparently has not occurred there for decades. These findings suggest that physical and hydrological conditions consistent with successful pallid sturgeon spawning exist within or upstream of these areas. What is not known is the exact location of spawning or the relative suitability of these conditions for the sturgeon. This inability to identify specific conditions that contribute to successful reproduction limits the ability of biologists to evaluate or define conservation or engineering criteria for habitat rehabilitation efforts specific to the needs of pallid sturgeon.

Objectives: Increased understanding of the reproductive physiology of these sturgeon and the ability to predict or assess relative reproductive success will increase the ability of managers to tailor prescribed management actions to promote species recovery.  To that end, the objectives of this study are to:

1. Determine the direction, magnitude, and habitat used during spawning migrations for shovelnose sturgeon and pallid sturgeon at two geographically and hydrologically distinct reaches of the lower Missouri River.

2. Describe the reproductive physiology of shovelnose sturgeon and pallid sturgeon prior to and after successful and unsuccessful spawning.

3. Identify and rank proximate cues necessary for successful spawning by Missouri River sturgeon.

4. Evaluate the effect that a semi-natural increase in flow has on the reproductive status, movements, and habitat use of pallid sturgeon shovelnose sturgeon.