If you run in saltwater, or even brackish water anti-fouling paint is probably a good idea.
If you run in freshwater exclusively, to my mind, why paint it?
All it does is add weight.
I have no idea what size your boat is but I remember reading about American Airlines back in the 1990's and how they were profitable at the time partly because they left their planes as mostly bare aluminum. Saved them 2.5 tons of weight per plane for 737's.
Obviously a 12-20 foot fisher is much smaller, but unless you have a compelling reason to paint it, why bother?
Unless you have life that wants to attach to your hull, there's no reason to do anything in my opinion. Paint is not the sort of thing I want on my boat keeping water out, so if that's what you want it for you need to do more work than painting her. On the other hand if there are snails/barnacles or anything else that want to live on your boat anti-fouling paint is a must. I've spent many hours of my life in my SCUBA gear under a boat scraping those darn lifeforms off the bottom of a dive boat.
If you just want to make your boat look sweet with a paint job, then by all means go for it. In that case, if running in freshwater exclusively I would look at a company like Rust-Oleum. In water where you want to keep things from attaching themselves to your boat (anti-fouling), I hear good things about this site: www.bottompaint.us .
Just my thoughts. I'm prolly wrong and it will be pointed out by someone far more experienced/knowledgeable than I am.
Good luck!