sea chub vs rudderfish

sea chub and rudderfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea chub	Yes	No	No	No
rudderfish	Yes	No	No	No

As nouns, rudderfish is a hyponym of sea chub; that is, rudderfish is a word with a more specific, narrower meaning than sea chub:

sea chub: schooling fishes mostly of Indian and western Pacific oceans; two species in western Atlantic
rudderfish: food and game fish around Bermuda and Florida; often follow ships

Other hyponyms of sea chub include Bermuda chub, Kyphosus sectatrix.

sea chub (noun)	rudderfish (noun)
schooling fishes mostly of Indian and western Pacific oceans; two species in western Atlantic	fish having the habit of following ships; found in North American and South American coastal waters
	food and game fish around Bermuda and Florida; often follow ships