Is a suckerfish a mammal

Hi, I just wanted to answer your question. No a sailfish is not a mammal. It is a fish and they breathe by gills, which I'm sure you are aware of. I am an avid whale fan and I've recently learned something that I had not thought about. The mammals of the waters have tails that are horizontal and the fish have tails that are vertical. A lot of people also tend to think that the whale shark is a mammal but in-fact it is not. I hope this has helped you. Sincerely, Tmlragland