smallmouth bass vs black bass

smallmouth bass and black bass both are nouns.

Word	Noun	Adjective	Verb	Adverb
smallmouth bass	Yes	No	No	No
black bass	Yes	No	No	No

As nouns, black bass is a hypernym of smallmouth bass; that is, black bass is a word with a broader meaning than smallmouth bass:

smallmouth bass: a variety of black bass; the angle of the jaw falls below the eye
black bass: widely distributed and highly prized American freshwater game fishes (sunfish family)

smallmouth bass (noun)	black bass (noun)
a variety of black bass; the angle of the jaw falls below the eye	widely distributed and highly prized American freshwater game fishes (sunfish family)
flesh of smallmouth bass	bluish black-striped sea bass of the Atlantic coast of the United States