pearlfish vs percoid

pearlfish and percoid both are nouns.

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

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

pearlfish: found living within the alimentary canals of e.g. sea cucumbers or between the shells of pearl oysters in or near shallow seagrass beds
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of pearlfish include percoid fish, percoidean.

pearlfish (noun)	percoid (noun)
found living within the alimentary canals of e.g. sea cucumbers or between the shells of pearl oysters in or near shallow seagrass beds	any of numerous spiny-finned fishes of the order Perciformes