fishworm vs oligochaete

fishworm and oligochaete both are nouns.

Word	Noun	Adjective	Verb	Adverb
fishworm	Yes	No	No	No
oligochaete	Yes	No	No	No

As nouns, oligochaete is a hypernym of fishworm; that is, oligochaete is a word with a broader meaning than fishworm:

fishworm: terrestrial worm that burrows into and helps aerate soil; often surfaces when the ground is cool or wet; used as bait by anglers
oligochaete: hermaphroditic terrestrial and aquatic annelids having bristles borne singly along the length of the body

Other hypernyms of fishworm include oligochaete worm.

fishworm (noun)	oligochaete (noun)
terrestrial worm that burrows into and helps aerate soil; often surfaces when the ground is cool or wet; used as bait by anglers	hermaphroditic terrestrial and aquatic annelids having bristles borne singly along the length of the body