Complex sentence: They reside in subpolar, temperate, and equatorial waters ranging throughout the Pacific and Southern Oceans, the southern Indian and Atlantic oceans, but are conspicuously absent in the north Atlantic.
Split into simpler sentences: They reside in subpolar, temperate, and equatorial waters throughout the Pacific and Southern oceans and the the southern Indian and Atlantic oceans. They are conspicuously absent in the north Atlantic.