Here is a thesis paper on crappie growth rates in Texas which you may or may not find the info you are after..LOL

The Age and Rate of Growth of the Black Crappie, Pomoxis Nigro-Maculatus (Le Sueur), and the White Crappie, Pomoxis Annularis Rafinesque, in the Koon Kreek Klub Lakes, Texas, Page: 48 | UNT Digital Library