porgy vs saltwater fish

porgy and saltwater fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
porgy	Yes	No	No	No
saltwater fish	Yes	No	No	No

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

porgy: lean flesh of fish found in warm waters of southern Atlantic coast of the United States
saltwater fish: flesh of fish from the sea used as food

porgy (noun)	saltwater fish (noun)
important deep-bodied food and sport fish of warm and tropical coastal waters; found worldwide	flesh of fish from the sea used as food
lean flesh of fish found in warm waters of southern Atlantic coast of the United States