Re: Catch and Release or...
You are almost right. You stated, "Biologically, it wouldn't matter if you harvested the big or small fish. The only limiting factor on fish growth is food." That's not correct. Genetics matters a lot. For example, you can have different strains of rainbows achieve a different average size given the same amount of limited food, just like you can have different sized people eating the same amount of food. Many biological factors can cause this.
And to take it further, when you have a relatively heavy amount of fishing pressure, you can change the gene pool to select for small fish if you only take out the large ones. This has been suggested as one of the reasons for the average decline in size of large mouth bass over the nation, and especially in Florida.
Back to the main point of this thread, yes, the biologists usually have it managed in favor of the "average" fisherman, and if they say you can keep a few fish, then feel free to do so. I usually don't.