Far more whales die in collisions with ships off the West Coast than ever wash up on beaches, a new study has found.
Every year, an estimated 18 blue whales, 22 humpback whales and 43 fin whales — all endangered species — perish off California, Oregon and Washington after being hit by ships.
But from 2006 to 2016, only 10 blue whales, 14 humpbacks and 11 fin whales — roughly one a year of each — were found dead on the West Coast shoreline and were confirmed to have been hit by ships.
The reason for the difference: The vast majority of dead whales sink. In many cases, the captains of the huge ships, often massive cargo vessels steaming between Asia and West Coast ports, don’t even know they have hit a whale, particularly at night.
In the years since commercial whale hunting was banned in the United States in 1972, ship strikes have become a leading source of whale deaths. That is a particular concern with blue whales, which remain endangered and have a population estimated at only about 1,800 off the West Coast.
“With small populations that are trying to recover, the deaths of even a few individuals can make a big difference,” said Cotton Rockwood, a co-author of the study and an ecologist with Point Blue Conservation Science, a non-profit scientific organization in Petaluma. “One individual that is killed could have an offspring every few years for decades. If they are lost, that is gone.”
The solution? New rules for how ships operate, the researchers said.
Rockwood, along with co-authors John Calambokidis of the Cascadia Research Collective in Olympia, Washington and Jaime Jahncke of Point Blue, recommends that commercial ships move farther from shore when passing by the West Coast. Shipping lanes at San Francisco Bay and Los Angeles should be adjusted, and areas of special concern marked on nautical charts, they say.
Most controversial, they suggest that ships slow down the closer they get to shore. There are currently voluntary programs around the Greater Farallones National Marine Sanctuary off the Marin County coastline, for example, where scientists radio ship captains when they see groups of whales and ask them to slow down. But the shipping industry has resisted mandatory speed limits on the open sea because it increases sailing time costs.
Industry leaders say they are amenable to discussing changes in the shipping lanes.
“In the same way that when you are driving down the highway and a deer jumps out in front of your car, nobody on a ship wants to hit a whale,” said John Berge, vice president of the Pacific Merchant Shipping Association in Oakland. “People on a ship are just like anybody else. If we can do things to reduce that risk we view that as a win.”
Berge said the industry has high compliance rates with voluntary speed limits, and has helped fund an app, called Whale Alert, to document the locations of whales. There is still some debate, he said, if changing speed reduces deaths, since ships weigh thousands of tons.
In May, a 79-foot blue whale washed up dead on Agate Beach in Bolinas. Biologists confirmed the whale, an adult female with 10 broken ribs, had been hit and killed by a ship.
Monday’s study, published in the scientific journal PLOS ONE, examined the locations of ship voyages from satellite tracking systems and overlaid them with whale information from tracking tags and surveys.
Rockwood said that after new speed limits, shipping lanes and other rules were put in place off the East Coast, deaths to endangered right whales fell roughly 70 percent.
“I don’t think we’ll ever get to zero, but we have some proven solutions from the East Coast,” he said. “They are very efficient and effective.”
