polly fish vs percoid

polly fish and percoid both are nouns.

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

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

polly fish: gaudy tropical fishes with parrotlike beaks formed by fusion of teeth
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of polly fish include percoid fish, percoidean.

polly fish (noun)	percoid (noun)
gaudy tropical fishes with parrotlike beaks formed by fusion of teeth	any of numerous spiny-finned fishes of the order Perciformes