User blog comment:Woohoot/The potential of Fishmen/@comment-3345720-20150708154150/@comment-3345720-20150710001559

Fishmen eating devil fruits would be a huge waste anyway. Being able to swim and breathe underwater is such an advantage for them.

Still not sure why fishmen who travel the world (fishman pirates, like Jinbe) wouldn't have acquired Haki by now, but who knows *shurg*