white shark vs mackerel shark

white shark and mackerel shark both are nouns.

Word	Noun	Adjective	Verb	Adverb
white shark	Yes	No	No	No
mackerel shark	Yes	No	No	No

As nouns, mackerel shark is a hypernym of white shark; that is, mackerel shark is a word with a broader meaning than white shark:

white shark: large aggressive shark widespread in warm seas; known to attack humans
mackerel shark: fierce pelagic and oceanic sharks

white shark (noun)	mackerel shark (noun)
large aggressive shark widespread in warm seas; known to attack humans	fierce pelagic and oceanic sharks