Sounds like a fun weekend!
I have no knowledge of the subject you are talking about except what I have read. But here is an old thread that might have some information to help you decide.
Pond carrying capacity If you read that thread and go with some assumption that you might have 400-500# of fish per acre in there (one third of that in your case because 1/3 acre), then that might give you an idea of what percentage you possibly could have already removed.
All conjecture on my part. Wait for the experts for a better answer. But that link might help you out in the mean time.
