It does have a large mouth. It is not a standard HBG IMO as it does not have the other traits of one. It could easily be a hybrid lepomis cross other than a HBG. Here is a thread on HBG and other crosses with loads of pics and info.

http://www.pondboss.com/forums/ubbthread...ite_id/1#import

And the sunfish archives (by Bruce) with pics.

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=92482#Post92482

And Shorty's recent thread (good pics and discussion) on hybrid lepomis.

http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=99961&fpart=1

A few of them should not cause a problem assuming you don't mind a few of their genes mixed in with your BG. What part of the country is the pond in ?