The researchers discovered that busy shipping lanes off Los Angeles and San Francisco overlap with the two areas of highest use by tagged blue whales off the U.S. West Coast during the summer and fall.
"This raises the specter of ship strikes," Irvine told Live Science.
To help save the whales, the researchers suggested moving the shipping lanes during the summer and fall, when the whales are most abundant. A similar relocation of shipping lanes in the Bay of Fundy, off eastern Canada, lowered the likelihood of vessels striking endangered right whales by an estimated 80 percent.
However, such a change "is not an easy thing that can be done quickly," Irvine said. "Shipping companies do not want to do anything that makes them go farther and use more fuel," he noted. "Also, in the case of Southern California, the U.S. Navy has training ranges all around the southern Channel Islands area, and if the shipping lanes were moved south of where they currently are, as we suggest, they would go near the training range, so the Navy would have to be consulted and agreeable to make this happen."
That being said, "it's in the shipping companies' interest to not hit whales," Irvine said. "When ships hit whales, the shipping companies' insurance companies require them to have their ships inspected for damage before they go across the ocean," Irvine added. "There are limited facilities to do that, and ships have to sit for a long time and miss out on income while they get inspected."
This means protecting the whales "is a win-win for everybody, and that's always good," Irvine said. "You take whatever reason you can get."
In the future, the scientists hope to use their data to help develop models predicting where blue whales might be. "We can use that data to help make the decision for a seasonal change or closure of shipping lanes," Irvine said.
The scientists detailed their findings online July 23 in the journal PLOS ONE.
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