food fish vs whitefish

food fish and whitefish both are nouns.

Word	Noun	Adjective	Verb	Adverb
food fish	Yes	No	No	No
whitefish	Yes	No	No	No

As nouns, whitefish is a hyponym of food fish; that is, whitefish is a word with a more specific, narrower meaning than food fish:

food fish: any fish used for food by human beings
whitefish: silvery herring-like freshwater food fish of cold lakes of the Northern Hemisphere

food fish (noun)	whitefish (noun)
any fish used for food by human beings	silvery herring-like freshwater food fish of cold lakes of the Northern Hemisphere
	flesh of salmon-like or trout-like cold-water fish of cold lakes of the Northern Hemisphere
	any market fish--edible saltwater fish or shellfish--except herring