lamprey vs sea lamprey

lamprey and sea lamprey both are nouns.

Word	Noun	Adjective	Verb	Adverb
lamprey	Yes	No	No	No
sea lamprey	Yes	No	No	No

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

lamprey: primitive eellike freshwater or anadromous cyclostome having round sucking mouth with a rasping tongue
sea lamprey: large anadromous lamprey sometimes used as food; destructive of native fish fauna in the Great Lakes

Other hyponyms of lamprey include Petromyzon marinus.

lamprey (noun)	sea lamprey (noun)
primitive eellike freshwater or anadromous cyclostome having round sucking mouth with a rasping tongue	large anadromous lamprey sometimes used as food; destructive of native fish fauna in the Great Lakes