Despite the fact that blue whales have a global distribution, they are sparsely populated around the world. Today, there are about 10,000 to 25,000 blue whales alive in the oceans, making them one of the most endangered whales. According to one estimate, the blue whales currently number around 8,000 to 9,000 animals. The largest concentration of these whales is found off California, numbering around 2,800 individuals.
Out of the two distinct sub-populations of blue whales in the North Pacific, the eastern North Pacific blue whales around the coasts of California appears to be the only population that is making a recovery. Today, these blue whales are believed to be around 2,000 individuals.
It is thought that during pre-whaling phase that lasted until 1967, there were about 250,000 blue whales alive in the oceans. In the Southern Hemisphere, during the period between 1904 and 1967, at least 350,000 blue whales were wiped out and they were literally brought to the brink of extinction.
About 29,000 individuals were exterminated in single season in the year 1931 alone. During the 20th century, a total of 360,000 blue whales were killed in the Antarctic.
Currently, there is lack of sufficient data with regards to the number of blue whales off the eastern North Atlantic. However, according to some data, the blue whales off Iceland are believed to be just 1,000 or even more.
Sources:
“Blue Whale”. WWF
“Blue Whale”. NOAA FISHERIES
“Blue Whale”. The Marine Mammal Center