(*) Tom, didn't you a few posts back applaud the insistence on not
writing "dinosaur" for "non-avian dinosaur," because such a usage
would be incorrect? And haven't you, in responding to me, just used
"fish" to mean "non-tetrapod fish"? (Grin!)
Maybe he used it to mean "actinopterygian". My thesis supervisor actually
_is_ on a crusade to change the meaning of "fish" to "actinopterygian" -- a
small change in terms of included species, a large one in terms of science!
After all, the meaning of "fish" has already shrunk since the days of
starfish, jellyfish and crayfish/crawfish*.
Besides, you wouldn't say "non-tetrapod fish" when you can say "non-tetrapod
gnathostome/vertebrate/...", right?
* ...which is actually a misinterpretation of French écrevisse, not a
deliberately coined compound with "fish".