fishing boat vs vessel

fishing boat and vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
fishing boat	Yes	No	No	No
vessel	Yes	No	No	No

As nouns, vessel is a hypernym of fishing boat; that is, vessel is a word with a broader meaning than fishing boat:

fishing boat: a vessel for fishing; often has a well to keep the catch alive
vessel: a craft designed for water transportation

Other hypernyms of fishing boat include watercraft.

fishing boat (noun)	vessel (noun)
a vessel for fishing; often has a well to keep the catch alive	a craft designed for water transportation
	an object used as a container (especially for liquids)
	a tube in which a body fluid circulates