Do I understand you correctly? The caviar of Dwarf sturgeons is among the best in thew world, and they have a breeding program? Where you referring to dwarf Sturgeons specifically or to a multitude of smaller sturgeons?
Pseudoscaphirhynchus hermanni Is the species I was referring to.
http://www.fishbase.org/summary/8764
They are quite rare due to habitat destruction if I remember correctly. Here is another dwarf stugeon that come in at about 18"
http://www.fishbase.org/summary/4634
Shovelnose sturgeon are widely bred in captivity for repatriation to it's former haunts. In some state they are still fished for commercially,One problem: Shovelnose sturgeons are protected species in most states make obtain them legally would be difficult. Another problem is you're claiming a 24" Shovelnose is rare in the wild, you're wrong we captured 50+ ones between 20-28" in a small section of the river in a single day. The Shovelnose might have good caviar, but they're less meaty and much armour than most sturgeons makes them less ideal candidate for aquaculture.
http://www.fishbase.se/summary/2596
for some reason a great many are also being shipped to China along with Polydon spathula.
http://www.fishbase.org/summary/174
Captive bred specimens are legal to keep in some states, other will require a permit.