That's a great question. I hope that several different people will answer with their own opinion.
To me a big bluegill is 9 inches or better, and a trophy bluegill would be about 10.5 inches or greater. That would vary a little bit based on the body condition. I've seen some 9.75 inchers that were in such supreme condition that they exceeded a pound, and those were more impressive than some bluegill that were 10.5 but not in good condition.
Any bluegill to me is a trophy when it hits the one pound mark.
I think that a big bluegill would fall in the 8"- 10" range and this is the size that I will occasionally keep to eat. I think that any bluegill that goes over 10 inches and/or a pound should be considered a trophy almost anywhere. For what it's worth, my own personal goal would be a 2-pounder or 12" bluegill or hybrid (I would'nt be too picky at that point). :)
Any bluegill over 9 inches is a nice bluegill in my book (and I never tire of harassing them with my 3-wt. flyrod), but there's a difference between "nice" and trophy-size. They cross over into the "big" category, for me, around 9-1/2 inches, and a true trophy would be at least a pound and a half or 11 inches. (Nebraska, incidentally, has a Master Angler program designating minimum threshholds for "memorable" fish of each game species; for bluegill it's 10 inches or one pound.)
We bought our present pond 3 years ago this weekend. Since then, I learned an incredible amount from the founder of this site, and a few of his friends. Now, in my fourth season with this pond, my idea of trophy bluegill has changed a lot.
Last night I took my flyrod down to my little half-acre pond. I caught 4 bluegill and a catfish that looked like a cartoon character. The state of West Virginia considers a bluegill greater than 10 inches, and more than 1 lb., to be a "citation" fish. All four of last night's bluegills would have qualified. For me, a trophy now has to be over 11 inches, and probably at least 1-1/2 pounds.
Maybe next season, it will be 11-1/2 inches, and 12 inches the year after that.
I look at thing a diffrent way, yes a big bluegill is 9 inches plus. Then you get to the "TROPHY" bluegill and I think that there is some consideration in this. My first bluegill on a fly rod was a "TROPHY" bluegill, but it was only 7 inches. I guess it all depends on your definition of "TROPHY". If you are just talking about size, depending on the location of the pond and if they have been feed. I would say a 10 1/2 or greater inch bluegill is a "TROPHY".
I know that it probably varies in each state and it varies probably even in different areas of each state but if you were to do everything right and were lucky, how long would it take on average for a bluegill to reach trophy size?
If you were to do everything right and get lucky, I think it can be done in 4 years.
If you do some things wrong, and if you get unlucky, if may never happen at all.
If I were to want to meet my magical ten inch mark, I would expect four full years in my region. There's an outside chance you could do it in three if you live in Texas. In more typical scenarios, I'd add two years.
Bruce using your "system" are you able to consistently raise trophy bluegill year after year or do they just happen when they happen. I am gaining respect for your abilities not only as an aquaculturalist but also as a fisherman. I still have not been able to raise a trophy size anything but am really enjoying trying. If it were easy it wouldn't be as fun.
I found that about every 2 or 3 years I'm seeing another really strong year class. Two years ago I was catching good numbers of 1 3/4 pound fish, but last year that particular year class evaporated, and I got very few over 1 1/4 lb.
As an old farm pond consultant in Ohio for the Division of Wildlife, I think there are two very important factors plus many others. The two are population density and water temperature. Over population usually causes stunting but can be controlled by heavy fishing, largemouth bass predation, and removing the excess with wire traps (plans for which I have committed to memory). Competition by other species can also have a deleterious effect on bluegill size. The white crappie usually does not help bluegills in a small pond, but, there are unexplained exceptions.
Another factor could be annual variations in invertebrates, such as cicadas, crayfish, etc.. Of course, drought and the opposite are important factors. Some things can be controlled and some cannot be controlled.