Why do delivery trucks carrying fish always have the word 'fish' printed on the back of the vehicle?

Question

I know you've seen these trucks driving around. Usually it's a white bobtail truck or some other white vehicle. Almost always in black print it will say fish on the side or back. Why? It's weird to me.

Answer 1

I dont know....something seems really fishy about that, lol

Answer 2

Things that make ya go hmmm.
If I ever have to haul fish, I'll make sure "beef" is printed on the truck