pollyfish vs percoid

pollyfish and percoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
pollyfish	Yes	No	No	No
percoid	Yes	No	No	No

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

pollyfish: 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 pollyfish include percoid fish, percoidean.

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