The professional tournament is the third tournament in original mode. It consists of 5 stages. You can catch and keep only your best 5 bass. There is a weight limit of 3 lbs for the bass you keep. As all tournaments, you have 3 sessions of 4 game hours to catch the fish per stage. Just try and catch the big and huge bass. If a smaller one bites, you can just let it go if you think it won't be your top 5 bass.
I never saw the computer go above 35 lbs in the tournament, so if you can get above 35 lbs, you should be good.