A few people at the NANFA forum are calling it straight WM. One of them has experience crossing WM and RES. Here's his comment:

 Quote:
I have made F1 warmouth female x redear male and redear female x warmouth male several times and redear^2 x warmouth. That is one of the few sunfish hybrids that is truely sterile. The fish you have appears to be a typical warmouth and based upon what I indicated previously, a F1 hybrid backcrossing into warmouth is unlikely.