California blue whale population up amid shipping lane, other threats


Blue whales are close to extinction, no thanks to whaling. California blue whales, however, surprisingly recovered “to near historical levels,” based on a recent research from the University of Washington (UW).

Study authors say such population going back to its near historical level justifies the slowdown in population growth recorded in recent years, beyond the idea of ship strikes.

The research also says the population of blue whales in the said state is the only one recognized to have rebounded from whaling. It adds that while the number of this species being struck by ships is possibly beyond the limits allowed by the U.S., the strikes have no immediate threat to the recovery.

“The recovery of California blue whales from whaling demonstrates the ability of blue whale populations to rebuild under careful management and conservation measures,” says lead author Cole Monnahan in a statement.

Blue whales are regarded as the biggest and heaviest animals on earth. These are close to 100 feet in length and weighs 190 tons as adults, which is double the biggest known dinosaur called Argentinosaurus.

Trevor Branch, an assistant professor of aquatic and fishery sciences at UW, says this species is “an icon of the conservation movement.”

California blue whales, to be specific, are said to be most visible when on feeding grounds around 20 to 30 miles off the coast of California, though these are really found by the Pacific Ocean’s eastern side, from the equator going up the Gulf of Alaska.

Based on monitoring of other groups undergoing the research, there are around 2,200 blue whales. This is probably 97 percent of the historical level based on the model used by the study’s co-authors.

A doctoral student in quantitative ecology and resource management at UW, Monnahan says the current numbers may appear to be low for some, but this is not so considering the number of California blue whales caught.

The study’s authors and co-authors earlier revealed at PLOS ONE journal an estimated catch of 3,400 California blue whales between the years 1905 and 1971.

Branch says when such estimated number is compared to the 346,000 blue whales caught close to Antarctica, it gives them idea how much smaller the California blue whales population possibly have been.

Research groups identified at least 11 ship strikes of blue whales by the U.S. West Coast, a rate that is beyond a “potential biological removal” of the 3.1 whales allowed yearly by the U.S. Marine Mammal Protection Act.

The study’s discoveries say that prior to a 50 percent possibility of the population dropping below the considered “depleted” level by regulators, there might be an increase of vessels by 11 fold.

Monnahan says their findings do not intend to deprive protection of California blue whales. A matter of fact, he says these whales are rebounding because of the actions are undertaken to start monitoring and prevent the catches. Without these actions, the population of this species could have been pressed close to extinction, which was unfortunately suffered by other populations of blue whales.

The study, 'Do ship strikes threaten the recovery of endangered eastern North Pacific blue whales?' was published in the Marine Mammal Science journal.

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