fish vs still-fish

fish is a noun but still-fish is not a noun.

Word	Noun	Adjective	Verb	Adverb
fish	Yes	No	Yes	No
still-fish	No	No	Yes	No

As verbs, still-fish is a hyponym of fish; that is, still-fish is a word with a more specific, narrower meaning than fish:

fish: catch or try to catch fish or shellfish
still-fish: fish with the line and bait resting still or stationary in the water

Other hyponyms of fish include crab, seine, scallop, scollop, rail, brail, angle, shrimp, net fish, shark, trawl, prawn.

fish (noun)	still-fish (noun)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills
the flesh of fish used as food

fish (verb)	still-fish (verb)
catch or try to catch fish or shellfish	fish with the line and bait resting still or stationary in the water
seek indirectly