fishing boat vs trawler

fishing boat and trawler both are nouns.

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

As nouns, trawler is a hyponym of fishing boat; that is, trawler is a word with a more specific, narrower meaning than fishing boat:

fishing boat: a vessel for fishing; often has a well to keep the catch alive
trawler: a fishing boat that uses a trawl net or dragnet to catch fish

Other hyponyms of fishing boat include dragger.

fishing boat (noun)	trawler (noun)
a vessel for fishing; often has a well to keep the catch alive	a fishing boat that uses a trawl net or dragnet to catch fish
	a fisherman who use a trawl net