Illegal Soviet whaling continued until 1971 when all whaling ceased" for blue whales, Branch told NBC News via email. Soviet secrecy 
 
 Writing in the journal, Marine Mammal Science, researchers from the University of Washington say the California blue whales are now at 97% of their historical levels. Whaling nations concentrated their hunting efforts on the colder waters of the Antarctic and until the practice was banned in 1966 some 346,000 of the animals were killed by harpoon. "Since then the population has been recovering steadily.” 
 
 Other groups have estimated that at least 11 blue whales are struck a year along the U.S. West Coast. The UW researchers calculate that there could be an eleven-fold increase in vessels before there is a 50 percent chance that the blue whale population will drop below what is considered "depleted" by regulators. "My impression is that they are fairly robust," said Cole Monnahan, also from the University of Washington and the lead author on the paper. "The recovery of California blue whales from whaling demonstrates the ability of blue whale populations to rebuild under careful management and conservation measures," Cole Monnahan, a UW doctoral student in quantitative ecology and resource management, said in a statement.
– After decades of deadly whaling, the California blue whale population has come back with a vengeance. A study in the Marine Mammal Science journal says that the once-endangered mammal, which can be found from Alaska all the way down to Costa Rica, has bounced back to "sustainable levels," with around 2,200 of the creatures now swimming in the Pacific surf right off the West Coast, reports the BBC. That growth spurt is due to meticulous conservation efforts—but also because the Russians aren't harpooning enormous numbers of them anymore. An estimated 346,000 California blue whales were harpooned before the practice was banned in 1966; between 1905 and 1971, about 3,400 were killed in the Pacific, mostly by Russian whalers. Despite the ban, Russians kept at it illegally until 1971—and as soon as they stopped, "the population has been recovering steadily," a University of Washington researcher tells NBC News via email. One major issue that still plagues blue whales: They keep getting smashed by ships, especially near California. Some groups estimate about 11 are hit each year, although scientists believe there would have to be an "elevenfold increase in vessels" before there's even a chance of the blue-whale population dipping to dangerously low levels. Meanwhile, they remain the largest animals on Earth, notes National Geographic. (Sorry, Dreadnoughtus.) Read how many calories a blue whale consumes in one gulp.