fish-fly vs fish fly

fish-fly and fish fly both are nouns.

Word	Noun	Adjective	Verb	Adverb
fish-fly	Yes	No	No	No
fish fly	Yes	No	No	No

As nouns, fish-fly and fish fly are synonyms defined as:

fish-fly and fish fly: similar to but smaller than the dobsonfly; larvae are used as fishing bait

fish-fly (noun)	fish fly (noun)
similar to but smaller than the dobsonfly; larvae are used as fishing bait	similar to but smaller than the dobsonfly; larvae are used as fishing bait