It's all too easy to find the subject of extinction a rather gloomy one, but there is good news as well as bad. Of all endangered animals, whales have attracted perhaps the best-known conservation efforts, and these have undoubtedly been partially effective. After hundreds of years of increasingly effective hunting, for their meat, blubber and other products, many species of whale were very close to extinction; by 1937 only 3% of the original right whale population remained, for example. After a 20-year ban on commercial hunting numbers have recovered to the point where humpback whales, for example, are now considered only 'vulnerable', rather than 'endangered'. But whales take a long time to mature and have offspring, which means their populations recover relatively slowly.
The population of blue whales in the antarctic seems to have recovered from a low of around only 500 animals 25 years ago to perhaps 1,500 now - but to give some idea of how tiny this number is compared to the original population, in one year alone (1929-30) whaling ships killed 30,000 blue whales in the same region.