Just go out in the days before the tournament, catch as many fish as possible, put them is your live box and select the largest for hiding in a cage somewhere out of the way.
On the day of the tournament, go to the spot, pick up the cage and "Viola!", instant day's catch.
Now, for lesson two - how to use Life Savers to cheating at golf......well maybe that's best kept a secret.
I'm guessing you could significantly improve your lie with a Life Saver. Is that what you are referring to?