https://www.worldwildlife.org/species/blue-whale

The blue whale is the largest animal on the planet, weighing as much as 200 tons (approximately 33 elephants). The blue whale has a heart the size of a Volkswagen Beetle. Its stomach can hold one ton of krill and it needs to eat about four tons of krill each day. They are the loudest animals on Earth and are even louder than a jet engine. Their calls reach 188 decibels, while a jet reaches 140 decibels. Their low frequency whistle can be heard for hundreds of miles and is probably used to attract other blue whales.

https://en.wikipedia.org/wiki/Blue_whale

Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over a century, they were hunted almost to extinction by whaling until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide,^[3] in at least five populations. The IUCN estimates that there are probably between 10,000 and 25,000 blue whales worldwide today.^[1] Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000).^[8] There remain only much smaller (around 2,000) concentrations in each of the eastern North Pacific, Antarctic, and Indian Ocean populations. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere. The Eastern North Pacific blue whale population had rebounded by 2014 to nearly its pre-hunting population.^[9]