stupid vs poor fish

stupid and poor fish both are nouns.

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

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

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

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

stupid (adjective)	poor fish (adjective)
lacking or marked by lack of intellectual acuity
lacking intelligence
in a state of mental numbness especially as resulting from shock