pike vs freshwater fish

pike and freshwater fish both are nouns.

Word	Noun	Adjective	Verb	Adverb
pike	Yes	No	No	No
freshwater fish	Yes	No	No	No

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

pike (noun)	freshwater fish (noun)
any of several elongate long-snouted freshwater game and food fishes widely distributed in cooler parts of the Northern Hemisphere	flesh of fish from fresh water used as food
medieval weapon consisting of a spearhead attached to a long pole or pikestaff; superseded by the bayonet
a broad highway designed for high-speed traffic
a sharp point (as on the end of a spear)
highly valued northern freshwater fish with lean flesh