fish vs aquatic vertebrate

fish and aquatic vertebrate both are nouns.

Word	Noun	Adjective	Verb	Adverb
fish	Yes	No	Yes	No
aquatic vertebrate	Yes	No	No	No

As nouns, aquatic vertebrate is a hypernym of fish; that is, aquatic vertebrate is a word with a broader meaning than fish:

fish: any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills
aquatic vertebrate: animal living wholly or chiefly in or on water

fish (noun)	aquatic vertebrate (noun)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills	animal living wholly or chiefly in or on water
the flesh of fish used as food

fish (verb)	aquatic vertebrate (verb)
catch or try to catch fish or shellfish
seek indirectly