Pond Boss Forums STOCKING A NEW POND Creating the food chain Delayed introduction of predator fish.

See this link for pictures of female hybrid bluegills (HBG) that are swollen with eggs. Note the gill flap shape and color of these females and compare it to that of male HBG. The males will often have an overall darker body hue and darker color on the gular area (breast). Males during spawning season are likely to have flat or slightly concave bellies. General body color in each pond will vary depending on water clarity. Generally clearer water results in darker body colors of both males and females. Cloudier water equals overall more subdued colors.

Thanks to Sparkplug for these good pictures.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=22297&Number=282644#Post282644

Probably the most reliable way to sex HBG is to see and sort them during spawning season when females are full of eggs as Sparkplug is doing in the link above.