gray mullet vs percoidean

gray mullet and percoidean both are nouns.

Word	Noun	Adjective	Verb	Adverb
gray mullet	Yes	No	No	No
percoidean	Yes	No	No	No

As nouns, percoidean is a hypernym of gray mullet; that is, percoidean is a word with a broader meaning than gray mullet:

gray mullet: freshwater or coastal food fishes a spindle-shaped body; found worldwide
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of gray mullet include percoid, percoid fish.

gray mullet (noun)	percoidean (noun)
freshwater or coastal food fishes a spindle-shaped body; found worldwide	any of numerous spiny-finned fishes of the order Perciformes
highly valued lean flesh of marine or freshwater mullet