gempylid vs percoid fish

gempylid and percoid fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
gempylid	Yes	No	No	No
percoid fish	Yes	No	No	No

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

gempylid: snake mackerels; elongated marine fishes with oily flesh; resembles mackerels; found worldwide
percoid fish: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of gempylid include percoid, percoidean.

gempylid (noun)	percoid fish (noun)
snake mackerels; elongated marine fishes with oily flesh; resembles mackerels; found worldwide	any of numerous spiny-finned fishes of the order Perciformes