The ocean is necessary for the blue whale's existence.
The blue whale ( Balaenoptera musculus ) is a marine mammal belonging to the baleen whales ( Mysticeti ) . B. m. indica , found in the Indian Ocean , may be another subspecies . Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century . Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence .