bottom fish vs groundfish

bottom fish and groundfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
bottom fish	Yes	No	No	No
groundfish	Yes	No	No	No

As nouns, bottom fish and groundfish are synonyms defined as:

bottom fish and groundfish: fish that live on the sea bottom (particularly the commercially important gadoid fish like cod and haddock, or flatfish like flounder)

bottom fish (noun)	groundfish (noun)
fish that live on the sea bottom (particularly the commercially important gadoid fish like cod and haddock, or flatfish like flounder)	fish that live on the sea bottom (particularly the commercially important gadoid fish like cod and haddock, or flatfish like flounder)