rough fish vs fish

rough fish and fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
rough fish	Yes	No	No	No
fish	Yes	No	Yes	No

As nouns, fish is a hypernym of rough fish; that is, fish is a word with a broader meaning than rough fish:

rough fish: any fish useless for food or sport or even as bait
fish: any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills

rough fish (noun)	fish (noun)
any fish useless for food or sport or even as bait	any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills
	the flesh of fish used as food

rough fish (verb)	fish (verb)
	catch or try to catch fish or shellfish
	seek indirectly