hairtail vs percoid fish

hairtail and percoid fish both are nouns.

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

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

hairtail: long-bodied marine fishes having a long whiplike scaleless body and sharp teeth; closely related to snake mackerel
percoid fish: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of hairtail include percoid, percoidean.

hairtail (noun)	percoid fish (noun)
long-bodied marine fishes having a long whiplike scaleless body and sharp teeth; closely related to snake mackerel	any of numerous spiny-finned fishes of the order Perciformes