silverside vs spiny-finned fish

silverside and spiny-finned fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
silverside	Yes	No	No	No
spiny-finned fish	Yes	No	No	No

As nouns, spiny-finned fish is a hypernym of silverside; that is, spiny-finned fish is a word with a broader meaning than silverside:

silverside: small fishes having a silver stripe along each side; abundant along the Atlantic coast of the United States
spiny-finned fish: a teleost fish with fins that are supported by sharp inflexible rays

Other hypernyms of silverside include acanthopterygian.

silverside (noun)	spiny-finned fish (noun)
small fishes having a silver stripe along each side; abundant along the Atlantic coast of the United States	a teleost fish with fins that are supported by sharp inflexible rays