smelt vs fish

smelt and fish both are nouns.

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

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

smelt (noun)	fish (noun)
small trout-like silvery marine or freshwater food fishes of cold northern waters	any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills
small cold-water silvery fish; migrate between salt and fresh water	the flesh of fish used as food

smelt (verb)	fish (verb)
extract (metals) by heating	catch or try to catch fish or shellfish
	seek indirectly