In addition to the above comments keep in mind that a variety of other factors come into play. Water quality , natural fertility, harvest and natural morts. That is why "it depends" is an often used comment here.

In the south using a 10/1 ratio with fertile water (natural or fertilized) and sup feeding you can keep balance for years if done correctly provided you have no major problems (increased morts - via fish kill , otters , cormorants , etc. ,over harvest , poor year class (bad spawn), drought).

Using a 30/1 ratio and the same situation you should be able to raise some trophies again depending on circumstances.

In short you have to match harvest with natural morts (predation mostly)and your conditions. A good guide is to not harvest lots of your biggest BG but harvest medium sized ones as long as you have lots of forage.