blennioid vs percoid fish

blennioid and percoid fish both are nouns.

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

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

blennioid: elongated mostly scaleless marine fishes with large pectoral fins and reduced pelvic fins
percoid fish: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of blennioid include percoid, percoidean.

blennioid (noun)	percoid fish (noun)
elongated mostly scaleless marine fishes with large pectoral fins and reduced pelvic fins	any of numerous spiny-finned fishes of the order Perciformes