What are the main ways to become a fishmonger?

I work in the meat department of a grocery store as a seafood Clerk (just handling selling, filling, keeping things fresh) and over time found I'm really interested in seafood, especially the actual processing of it. I want to try to learn how to be and become a fishmonger but I don't exactly know how, I know with our meat cutters they have their own apprenticeship program but do said programs exist for seafood? Any forms of education?