Since whaling was banned in 1966, California blue whale numbers have rebounded to 97 percent of historic levels, a new study shows.
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Researchers from the University of Washington say that California blue whales—the largest animals on planet Earth— have made a robust recovery from decades of whale-hunting. They estimate the population is now at 97 percent of their historic levels. The study is published in the journal Marine Mammal Science.
First, the researchers had to figure out the historic levels of the blue whale populations by looking at the numbers killed through whaling before the practice was banned in 1966.
Until whale-hunting was banned, some 346,000 of the magnificent creatures were slaughtered, mostly concentrated in the Antarctic, where the whale population is only at one percent of its historic level. A lot of the whaling was done by Russian fleets, but because most of the information on the catches was kept secret under the old Soviet regime, scientists have only recently had access to this data, BBC News reports.
One difficulty was in distinguishing between the two distinct blue whale populations, the California group and others living close to Russia and Japan. To accomplish this, the researchers used whale-song.
“We were trying to separate the catches into east and west, but we didn’t know the boundary between the two,” said co-author Dr. Trevor Branch from the University of Washington in a report by BBC News. “So we used the current locations of where they sing to figure out the dividing line. Their repetitive calls are different.”
Once the scientists were able to calculate the numbers of blue whales lost to whaling, they could figure out the historic population.
At 97 percent of their historic numbers, the team thinks the increase in blue whale populations may have slowed as reach the ocean’s capacity to support them. One remaining concern at the moment are the dangers to whales from being hit by ships. In California, authorities are so concerned they now are paying commercial shipping operators to slow down.
“California blue whales are recovering because we took actions to stop catches and start monitoring,” said lead author Cole Monnahan, also from the University of Washington. “If we hadn’t, the population might have been pushed to near extinction—an unfortunate fate suffered by other blue whale populations.”