27.  LOWER MISSOURI RIVER SPRING RISE:  SOME FACTORS RELATED TO PALLID STURGEON SPAWNING

Donald G. Jorgensen* Missouri River Technical Committee of the Siouxland Chamber of Commerce, 101 Pierce Street, Sioux City, IA 51101; Phone 605-966-5645; donjorg@longlines.com

The advisability of a spring rise by regulating the flow from Gavins Point Dam was evaluated.  Some of the factors considered included:

• Applicability of the flood pulse concept for restoration of the pallid sturgeon.
• Evaluating existing spring rises in the reach in reference to temperature and flow for both existing and historic conditions.
• Observations about sturgeon spawning in relation to hydrology, temperature, and photoperiod.
• Observations of sturgeon behavior in the free embryo and early larval stage.
• Historic observations of sturgeon spawning in the Mississippi Basin.
• Cues related to sturgeon migration and movement.

Conclusions include that a spring rise is not likely essential in relation to sturgeon pre- spawning and spawning behavior. Pallid sturgeon recruitment is slight to non-existent in the Lower Missouri River, even though spring rises are common in a significant portion of the reach. This suggests that factors other than a spring rise are resulting in lack of recruitment. New research indicates sturgeon are likely to spawn after a minimum photoperiod is obtained and after the correct temperature is obtained. The correct bottom- water velocity at the spawning site is needed if successful spawning leading to recruitment is to be achieved.