First, a disclaimer: I'm not a pro, I have no sponsors and have never fished a tournament.
I don't know if studying business will give you a "1-up", but you should know business, period. After all, pro fishermen aren't employees, they're independent contractors running their own businesses. So it's obvious that business skills are needed, as are marketing skills. You need to market yourself to potential sponsors, and if you have sponsors, you need those skills to promote your sponsors' products. And communication skills are a must, not just for a fisherman, but for just about anything you do with your life.
This is just speculation, but I would guess that getting sponsors is similar to getting a job. There may be 100s of applicants for one position and everyone wants to be sponsored, but there are a limited number of sponsor dollars available, so you need to demonstrate why you should get those dollars rather than the many people you're competing with. See above for the skills that might help you do that.
Good luck.