pike vs pickerel

pike and pickerel both are nouns.

Word	Noun	Adjective	Verb	Adverb
pike	Yes	No	No	No
pickerel	Yes	No	No	No

As nouns, pickerel is a hyponym of pike; that is, pickerel is a word with a more specific, narrower meaning than pike:

pike: any of several elongate long-snouted freshwater game and food fishes widely distributed in cooler parts of the Northern Hemisphere
pickerel: any of several North American species of small pike

Other hyponyms of pike include Esox lucius, northern pike, Esox masquinongy, muskellunge.

As nouns, pickerel is a hyponym of pike; that is, pickerel is a word with a more specific, narrower meaning than pike:

Other hyponyms of pike include muskellunge.

pike (noun)	pickerel (noun)
any of several elongate long-snouted freshwater game and food fishes widely distributed in cooler parts of the Northern Hemisphere	any of several North American species of small pike
medieval weapon consisting of a spearhead attached to a long pole or pikestaff; superseded by the bayonet	flesh of young or small pike
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