bottom-feeder vs mullet

bottom-feeder and mullet both are nouns.

Word	Noun	Adjective	Verb	Adverb
bottom-feeder	Yes	No	No	No
mullet	Yes	No	No	No

As nouns, mullet is a hyponym of bottom-feeder; that is, mullet is a word with a more specific, narrower meaning than bottom-feeder:

bottom-feeder: a fish that lives and feeds on the bottom of a body of water
mullet: bottom dwelling marine warm water fishes with two barbels on the chin

bottom-feeder (noun)	mullet (noun)
a fish that lives and feeds on the bottom of a body of water	bottom dwelling marine warm water fishes with two barbels on the chin
a scavenger that feeds low on the food chain	freshwater or coastal food fishes a spindle-shaped body; found worldwide
	highly valued lean flesh of marine or freshwater mullet