A pure strain bluegill will have a completely all black "ear" or opercule flap. If there is any margin or thin boarder membrane on the back or lower edge of the ear flap other than black it is probably a hybrid or green sunfish. Others can refer you to a website with good pictures. I can email you pretty good pictures of bgill (male & female) and hybrid bgill if you send me your email address. Our ponds that had open water, are froze up again this week, do you still have open water?

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management