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California Blue Whales Make a Comeback: Species Rebounds to Near Historical Levels

First Posted: Sep 05, 2014 11:02 AM EDT

California blue whales are making a comeback. Scientists have found that the number of these whales has rebounded to near historical levels, which is good news when it comes to the conservation of this species.

Blue whales had been nearly hunted to extinction in the past. Nearly 100 feet in length and weighing a staggering 190 tons as adults, blue whales are the largest animals on Earth. They're their most visible while at feeding grounds 20 to 30 miles off of the coast of California, but they can also be found along the eastern side of the Pacific Ocean from the equator up into the Gulf of Alaska.

Currently, there are about 2,200 blue whales. In order to find out how this matched up against historical levels, the researchers examined catches of blue whales. Scientists teased out numbers from Russian whaling archives. Then, they used acoustic calls produced by the whales to separate the catches taken from the California population from whales taken in the western Northern Pacific near Japan and Russia. This allowed the scientists to model the California blue whale population over time.

So what did they find? It turns out that California blue whales are at about 97 percent of the historical level. While this may seem like a low number, it's not really when considering that the California population has historically always been smaller than the ones near Antarctica.

So what does this mean for the whales? It's good news. It means that ship strikes are likely not to cause overall population declines. It also explains why there's been a slowdown in population growth, since blue whales are already near historical levels.

"We think the California population has reached the capacity of what the system can take as far as blue whales," said Trevor Branch, one of the researchers, in a news release.

The findings reveal how much of a conservation success story blue whales truly are. That said, monitoring is likely to continue in order to make sure that the population remains stable far into the future.

The findings are published in the journals PLOS One and Marine Mammal Science.

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