Statement of Problem:
Pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus), are endemic to the Missouri and Mississippi Rivers. The pallid sturgeon is very rare and considered endangered. The shovelnose sturgeon is threatened by commercial over-harvest and has been extirpated from portions of its range but is common enough to be used as a surrogate for the pallid sturgeon. Investigators have determined that migratory behavior, population structure, and physiological condition of Russian sturgeon have been altered by flow regulation and hydrological changes in riverine systems (Dettlaff et al. 1993). Both the Missouri and Mississippi rivers have experienced these types of changes. Consequently, habitat alteration and destruction are presumably major limiting factors for both pallid and shovelnose sturgeon. Little is known about the life history and biology of these two sturgeon species. The endangered status of the pallid and eminent threat of commercial over-harvest and need for reintroduction of the shovelnose sturgeon into parts of its range make it imperative that their biology be quickly understood. Recovery efforts require information on the reproductive physiology of pallid sturgeon and the influence of environmental variables on sexual maturation and spawning. Methods are needed to assess the reproductive status of pallid sturgeon so as to develop and evaluate management strategies to enhance spawning of pallid sturgeon in the Missouri river and in artificial propagation programs. Successful hatchery production has given biologists some hope that extinction for the pallid sturgeon can be avoided and that the shovelnose and pallid sturgeons can be reintroduced in areas where they have been extirpated. To minimize impacts on natural populations, methods must be developed that permit study and monitoring of shovelnose and pallid sturgeons that are non-lethal and minimally stressful.
Objectives:
1. Develop methods to use endoscopy and ultrasonic imagery to visually observe the gonads of adult and immature shovelnose and pallid sturgeon.
2. Develop steroid profiles for several sex-steroids important in gametogenesis and gonadal maturation. By developing temporal steroid profiles in tandem with the imagery measurements we intend to validate the results from the images.