Here's the reply I got from the site. Read the article outlined here and it basically says they tried to mix four different species sperm with channel eggs and did so successfully with all four to include the flathead catfish.
Journal of Applied Aquaculture (ISSN: 1045-4438)
Volume: 3 Issue: 3/4
Early Growth and Morphology Among Hybrids of Ictalurid Catfishes
Page Range: 235 - 256
DOI: 10.1300/J028v03n03_03
Cheryl A. Goudie, Terrence R. Tiersch, Bill A. Simco, Kenneth B. Davis, Qinghua Liu
I also thought I remembered some research by Rex Dunham at Auburn University, but I didn't actually see that reference when I looked back at my notes (he did work with channel x blue). You may find it with a Google search or in one of the journal searches.
Good Luck and Good Fishing...
Bob Wattendorf
Marketing and Special Projects Coordinator/WebMaster
Freshwater Fisheries Management
620 South Meridian St.
Tallahassee, FL 32399-1600
Phone: 850/488-0520
Fax: 850/413-0381
Mobile: 850/528-1060
Website: MyFWC.com/Fishing