white mullet vs gray mullet

white mullet and gray mullet both are nouns.

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

As nouns, gray mullet is a hypernym of white mullet; that is, gray mullet is a word with a broader meaning than white mullet:

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

Other hypernyms of white mullet include grey mullet, mullet.

white mullet (noun)	gray mullet (noun)
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