Experts are proposing changes to shipping lanes off the coasts of Los Angeles and San Francisco, at least during summer and fall seasons, in order to reduce the number of whale deaths caused by collisions with large vessels.
According to a study recently published in the journal PLOS ONE, researchers attached transmitters to 171 blue whales found off the coast of California at various times between 1993 and 2008.
These transmitters allowed experts to track whale distribution during various seasons, determining where exactly the massive creatures went to feed.
"The main areas that attract blue whales are highly productive, strong upwelling zones that produce large amounts of krill - which is pretty much all that they eat," lead author Ladd Irvine said in a public release. "The whales have to maximize their food intake during the summer before they migrate south for the winter, typically starting in mid-October to mid-November."
Thanks to funding from the Office of Naval Research, the National Science Foundation and the National Geographic Society, along with significant funding from various universities and private parties, this is reportedly the most comprehensive study of blue whale travel patterns ever conducted.
And the study reports some striking findings. About one fourth of the worlds estimated 10,000 blue whales were found to be spending time in the waters off the West Coast, primarily feeding in areas that unfortunately put them in the direct paths of shipping vessels.
"Blue whales may not be as acoustically aware as species that rely on echolocation to find prey," explained Bruce Mate, who directs the Marine Mammal Institute at OSU's Hatfield Marine Science Center in Newport, Ore. "There is some evidence that the location of the engines in the rear of the ship creates something of an acoustic shadow in front of them, making it hard for whales to hear the ship coming."
However, the study's authors argue that simply adding a warning noise to these ships could do more harm than good.
"Putting some kind of noise deterrent on the ships isn't really an option," Mate said. "You don't really want to drive endangered whales out of their prime habitat and best feeding locations."
So what can be done? The researchers argue that moving the shipping lane "would not be unprecedented" and could potentially lead to a drop in whale collisions by a whopping 80 percent.
"It's not really our place to make management decisions, but we can inform policy-makers and in this case it is pretty straightforward," added co-author Daniel Palacios. "You will eliminate many of the ship strikes on blue whales by moving the shipping lanes south of the northern Channel Islands."
The study can be found published in PLOS ONE on July 23.