California Blue Whales Making a Comeback
California blue whales are making a comeback, and have recovered to near historic numbers, according to scientists.
Despite concerns about the number of ship strikes off the California coast, blue whales in this region are now estimated at 2,200, up from a low of 951 in 1913, according to University of Washington researchers.
This is the only population of blue whales known to have recovered from whaling, which almost drove the species to extinction.
"The recovery of California blue whales from whaling demonstrates the ability of blue whale populations to rebuild under careful management and conservation measures," lead author Cole Monnahan of the University of Washington, said in a statement.
While 2,200 may seem rather low, it's actually 97 percent of historic levels, and a great success story considering how many California blue whales were once hunted. According to the new study, published in the journal Marine Mammal Science, approximately 3,400 of these marine giants were caught between 1905 and 1971.
Blue whales - nearly 100 feet in length and weighing 190 tons as adults - are the largest animals on Earth. While they are often seen feeding 20 to 30 miles off the California coast, they are actually found along the eastern side of the Pacific Ocean from the equator up into the Gulf of Alaska.
The research team used multiple methods to estimate current population numbers, including acoustic data from their whaling calls. This allowed them to distinguish between California blue whales and those belonging to another population in waters off of Japan and Russia.
Still, one major concern among scientists is the issue of ship strikes, most of which happen off the California coast.
There are likely at least 11 blue whales struck a year along the US West Coast, according to previous studies. This new data suggests that there could be an 11-fold increase in ships before there is a 50 percent chance that the population will drop below what is considered "depleted" by regulators.
"Even accepting our results that the current level of ship strikes is not going to cause overall population declines, there is still going to be ongoing concern that we don't want these whales killed by ships," said co-author Trevor Branch.
"California blue whales are recovering because we took actions to stop catches and start monitoring," Monnahan added. "If we hadn't, the population might have been pushed to near extinction - an unfortunate fate suffered by other blue whale populations."