stupid person vs poor fish

stupid person and poor fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
stupid person	Yes	No	No	No
poor fish	Yes	No	No	No

As nouns, stupid person and poor fish are synonyms defined as:

Other synonyms of stupid person include dolt, dullard, pillock, pudden-head, pudding head, stupe, stupid.

stupid person (noun)	poor fish (noun)
a person who is not very bright	a person who is not very bright