trawler vs fishing vessel

trawler and fishing vessel both are nouns.

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

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

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

Other hypernyms of trawler include fishing boat, fishing smack.

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