User blog comment:Woohoot/The potential of Fishmen/@comment-3345720-20150708154150/@comment-142.51.108.254-20150708225658

Otohime and Shirahoshi both did.

Personally, I think that most merfolk/fishmen would focus more on their water manipulation ability than on training busoshoku haki, especially if it turns out to be impossible to imbue water with haki. If the two don't work well together, then underwater combat would be an obvious benefit for them.

I highly doubt that they'd be unable to use buso, since we might already have witnessed some using the non-visible buso, and since "anyone who trains hard enough" can learn buso or kenbun.

It's just Haoshoku that's notable. Based solely on strength of character, it's possible that Fisher Tiger did, but had not awakened it before his death.