silverside vs jacksmelt

silverside and jacksmelt both are nouns.

Word	Noun	Adjective	Verb	Adverb
silverside	Yes	No	No	No
jacksmelt	Yes	No	No	No

As nouns, jacksmelt is a hyponym of silverside; that is, jacksmelt is a word with a more specific, narrower meaning than silverside:

silverside: small fishes having a silver stripe along each side; abundant along the Atlantic coast of the United States
jacksmelt: a relatively large silversides of the Pacific coast of North America (known to reach 18 inches in length)

Other hyponyms of silverside include Atherinopsis californiensis.

silverside (noun)	jacksmelt (noun)
small fishes having a silver stripe along each side; abundant along the Atlantic coast of the United States	a relatively large silversides of the Pacific coast of North America (known to reach 18 inches in length)