Despite decades of protection from hunting and commercial fishing, the world's population of blue whales has dwindled from hundreds of thousands to just 10,000 today, one quarter of which live in the northeastern Pacific Ocean off the West Coast of the United States.
Now new research suggests that small adjustments to shipping lanes approaching San Francisco and Los Angeles could vastly improve the long-term survival not only of individuals but of the species as a whole.
In the most comprehensive study of any whale species ever undertaken, marine biologists tracked 171 blue whales over 15 years. The researchers mapped their migration patterns in relation to existing shipping lanes, and identified two key areas where shipping traffic bisect major feeding waters and present a high hazard for collision. They published their findings Wednesday in the peer-reviewed, open-access journal PLOS ONE.
Marine biologists know very little about the habits of blue whales, says Bruce Mate, director of the Marine Mammal Institute at Oregon State University in Newport, Ore. and lead author of the study.
“The first time we ever found a known place where they gather to breed and calve was 2009,” Professor Mate says. “That shows how hard these animals are to study.”
However, new technology has given Mate and his colleagues new opportunities to observe these notoriously elusive creatures. He and his team were able to track dozens of individuals using satellite tags that have only become available for widespread use since the turn of the century. These tags send pings to satellites, which orbit the earth every 100 minutes. A satellite picks up the signal and, based on the frequency of the sound retrieved, technicians can determine the tag’s orientation to the satellite at the time of transmission. The tags don’t transmit a signal while the whale is underwater, so there is a certain degree of chance that the whale will happen to surface when the satellite is in position to accept the ping.
Mate and his colleagues were able to map that data and locate key feeding grounds where whales seem to return year after year. Blue whales feed almost exclusively on krill, small, shrimp-like creatures that are less than an inch long. Areas with large concentrations of krill tend to be where an upcurrent draws cold, nutrient-rich water from the ocean bottom. They also tend to be near bays where a series of rivers dump vital nutrients into the ocean. That’s where collisions with shipping vessels tend to occur.
Because their preferred food is so tiny and tends to disappear during winter months, they must consume massive quantities of krill when it is available. During the spring, summer, and fall months, these ocean behemoths do little else but look for food and eat, says Regina Asmutis-Silva, executive director of the Whale and Dolphin Conservation in Plymouth, Mass.
Like most whales, “if blue whales are eating, they are fairly oblivious to anything else. They’re not looking out for ships,” says Ms. Asmutis-Silva. “Even if they heard a ship coming, if they have to choose between moving out of the way and eating food to survive, they are going to keep eating.”
Mate and his colleagues identified San Francisco Bay and around the Channel Islands as the two key areas off the West Coast where ships are bisecting these feeding grounds. The scientists suggest in their paper that a slight shifting of these shipping lanes could drastically decrease the risk of collision with a blue whale.
Canadians have undertaken similar efforts in the Bay of Fundy near New Brunswick to help reduce collisions with the extremely endangered North Atlantic right whale. Those efforts appear to have been enormously successful, says Moira Brown, a senior scientist with the New England Aquarium and an expert on North Atlantic right whales.
“The only evidence that we can go on are whale carcasses. That’s how we discovered this problem in the first place,” Ms. Brown says. “As far as we know there have been no ship strikes in the Bay of Fundy since the shipping lanes were changed in 2003.”
Mariners voluntarily submitted to the change in the Bay of Fundy, in part, because there was room to maneuver around the whales.
Similar efforts have been undertaken in Boston Harbor and off Cape Cod, but that’s not feasible everywhere, Brown says. Along the US East Coast, there are several areas where the whale’s migration patterns are directly perpendicular to shipping lanes and cannot be avoided. In those instances, the US has opted to impose speed rules to slow the ships down during the months when the whales are most prevalent.
Establishing similar accommodations for blue whales on the West Coast is further complicated by the presence of the US military. The Department of Defense and the Navy perform exercises in both the San Francisco Bay and near the Channel Islands. That said, the Navy has been extremely instrumental in the development of the necessary technology to further research into the needs of these and other marine creatures.
“We can make recommendations for what we think will help these whales,” Mate says. “But this is as much about political process as it is about biological process.”
While this research highlights the importance of the coast of California in the preservation of the blue whale, the issue is truly global, says Asmutis-Silva.
Blue whales can be found all over the world. There is a population off the coast of Sri Lanka whose feeding waters also are traversed by shipping lanes, she says. Organizations in the United States have the means to finance the necessary research to develop scientifically-informed mitigation measures. However, in other parts of the world, such as Sri Lanka, such funding is much harder to come by.
“I think the world often looks at us to see what can be done. If we can look at the problem of whale strikes here and show that there’s potential for reducing them, then maybe that strategy can be used elsewhere,” she Asmutis-Silva says.