Usually this question would be posed for one of two reasons.
1. Management purposes--in order to influence size structure or population dynamics of bluegill, competing species, or predator species that utilize bluegill as forage.
2. Dinner table management--the person posing the question likes to eat bluegill.
I think that if you fall in the latter category, then a good way to protect your population would be to identify a group of fish that you can put heavy pressure on. Using this forum, you could learn to ID bluegill by sex and pressure females, or you could pick a slot, such as 6-8 inches, and harvest these fish. I believe that in a body of water this large that if you kept only females or 6-8 inch fish, then you and several friends could harvest as many fish as you can catch without guilt or danger to the population.
If you fall into the former category, then the question is considerably more complex and might be better answered by Greg, Bill or Cecil.
Annual growth of bluegill and their maximum age are together linked by geographic and climatological factors. In warmer climes bluegill can grow to six inches in the first year and as much as nine inches by the second year. In cooler areas this could take as many as six years to reach the nine inch size. Around here a bluegill that reaches age-10 is an old warrior, but a fish this old would be unheard of in south Georgia or Florida. In Minnesota an age-10 fish might have some pretty good years left in him. Some people believe that cold blooded animals such as fish, age as a function of degrees in excess of freezing multiplied by the number of minutes spent at said temperture. This has also been a subject of speculation on this forum. Good question--vague answers. Sorry about drifting a little bit.
