largemouth black bass vs largemouthed black bass

largemouth black bass and largemouthed black bass both are nouns.

Word	Noun	Adjective	Verb	Adverb
largemouth black bass	Yes	No	No	No
largemouthed black bass	Yes	No	No	No

As nouns, largemouth black bass and largemouthed black bass are synonyms defined as:

largemouth black bass and largemouthed black bass: a large black bass; the angle of the jaw falls behind the eye

Other synonyms of largemouth black bass include largemouth, largemouth bass, largemouthed bass, Micropterus salmoides.

largemouth black bass (noun)	largemouthed black bass (noun)
a large black bass; the angle of the jaw falls behind the eye	a large black bass; the angle of the jaw falls behind the eye