Study: Blue whales have recovered to pre-hunting levels off U.S. West Coast

In the early 20th century, people hunted the blue whale to near extinction. In some rare good news for the world's largest known inhabitant, the population of blue whales off the U.S. West Coast has rebounded to near pre-whaling days, according to a study published online Friday in the journal Marine Mammal Science.

There are now about 2,200 blue whales from Alaska to Mexico, up from about 750 in the 1930s, and the new study says that the current population is about 97 percent of its pre-hunting levels. "For us, this is a great conservation success story," says Cole Monnahan, a doctoral student at the University of Washington. "We caught way too many whales from this population, but when we left them alone, they recovered."

The model used by Monnahan and his colleagues estimated the 1905 pre-whaling population by studying records of how many California blue whales were killed in the 20th century. Some experts say the number they landed on, 3,400, is probably too low, throwing into doubt the researchers' conclusion that the blue whale population is about back to the level this part of the ocean can support.

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Still, nobody disputes that the California blue whale's recovery is real, and a rare success story: Chile's blue whale population is at about 10-20 percent of historical levels, says the University of Washington's Trevor Branch, and the once-huge population in Antarctica — about 240,000 whales — is 1 percent of its former size. The International Whaling Commission prohibited hunting blue whales for commercial purposes in 1966, but the massive whales are still poached, killed by pollution, or run over by ships — about 11 blue whales are killed by ships off the West Coast each year.