(In order of book introduction)
"There appeared in the papers caricatures of every gigantic and imaginary creature, from the white whale, the terrible "Moby Dick" of sub-arctic regions, to the immense kraken..." Ch. 1
The white whale is more commonly known as the Beluga whale and, as M. Arronax suggests, resides in the Arctic and sub-arctic regions of the sea. The Beluga and the narwhal are the only two cetacea belonging to the Monodontidae family (Wikipedia).