mullet vs white mullet

mullet and white mullet both are nouns.

Word	Noun	Adjective	Verb	Adverb
mullet	Yes	No	No	No
white mullet	Yes	No	No	No

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

mullet: freshwater or coastal food fishes a spindle-shaped body; found worldwide
white mullet: silvery mullet of Atlantic and Pacific coasts

Other hyponyms of mullet include Mugil cephalus, striped mullet, Mugil curema, liza, Mugil liza.

mullet (noun)	white mullet (noun)
bottom dwelling marine warm water fishes with two barbels on the chin	silvery mullet of Atlantic and Pacific coasts
freshwater or coastal food fishes a spindle-shaped body; found worldwide
highly valued lean flesh of marine or freshwater mullet