fisher vs marten cat

fisher and marten cat both are nouns.

Word	Noun	Adjective	Verb	Adverb
fisher	Yes	No	No	No
marten cat	Yes	No	No	No

As nouns, marten cat is a hypernym of fisher; that is, marten cat is a word with a broader meaning than fisher:

fisher: large dark brown North American arboreal carnivorous mammal
marten cat: agile slender-bodied arboreal mustelids somewhat larger than weasels

Other hypernyms of fisher include marten.

fisher (noun)	marten cat (noun)
large dark brown North American arboreal carnivorous mammal	agile slender-bodied arboreal mustelids somewhat larger than weasels
someone whose occupation is catching fish