Are sailfish warms blooded like Tuna? No. Tuna are not warm blooded, and neither are sailfish. The only warm blooded fish discovered to date is the opah. [1] 1. Opah, the first truly warm-blooded fish | EarthSky.org. read more
Since 2015 the opah is the only full warm blooded fish. Tunas are warm blooded, just not fully, meaning their core is warm blooded. Kinda like duck feet, which have a heat transfer system. read more
The only Warm-blooded fish we yet know of are Sharks. Even then, only certain shark species, like the Great White and Greenland sharks, are known to be warm blooded. There are no warm blooded freshwater fish that I, at least, am aware. read more
Warm blooded animals maintain a constant body temperature that is controlled by metabolic heat production. Cold-blooded animals eg. fish do not. The opah is very good at conserving heat generated within muscles but does not generate heat metabolically in order to maintain a constant internal body temperature regardless of external water temperature. read more