Some Classes in college you can take are Ichthyology, yes that is a class but not many colleges have it, the one I'm going to is in Florida and it has it.
You can also take Meristics, Marine Biology, Fisheries science(for farming fish), limnology, hydrobiology, and aquatic ecosystem.
A lot of these classes are very hard to find because a lot of colleges simply don't have them a fund a few in Florida that have a lot of these classes look around. Some may not apply but extra classes is always good. Hope i spelled them right.
But on top of it all look into Being a Ichthyologist do research because it is not easy and most live off of grants witch can be good and bad in a way.
Good luck i want to be one also
EDIT:Just noticed you live in Florida, lucky you i live in New York, a lot of Florida colleges have ichthyology classes.