lingcod vs saltwater fish

lingcod and saltwater fish both are nouns.

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

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

lingcod: the lean flesh of a fish caught off the Pacific coast of the United States
saltwater fish: flesh of fish from the sea used as food

lingcod (noun)	saltwater fish (noun)
food fish of the northern Pacific related to greenlings	flesh of fish from the sea used as food
the lean flesh of a fish caught off the Pacific coast of the United States