Whales are showing up in San Francisco Bay. New ship alerts could help protect them

Gray whales are showing up in San Francisco Bay, a detour on their long migrations from Mexico to Alaska. They seem to be searching for food, as changing ocean conditions reduce availability of their normal prey in the Arctic. Darrin Allen/The Marine Mammal Center, NOAA hide caption

Gray whales used to be a rare sight in San Francisco Bay. Now, their spouts are appearing off Alcatraz Island in one of the busiest waterways in the country.

The whales are making a pitstop on their long migrations from Mexico to Alaska, detouring under the Golden Gate bridge for a snack as climate change is shrinking their normal food supply in Arctic waters.

But as gray whales try to adapt to one human-caused impact by feeding in San Francisco Bay, it's putting them squarely in the path of another hazard: ships.

Of 16 gray whales seen in San Francisco Bay this year, seven have died. Researchers have found evidence that several were killed by ship strikes.

With some whales now hanging out in the bay for weeks, a coalition of marine scientists and local officials are trying out a new system to prevent collisions.

Researchers installed a thermal camera on an island in the bay that can spot heat from the whales' exhalations. Potential whale sightings are screened by artificial intelligence and then confirmed by human screeners. The U.S. Coast Guard can then use that information to alert vessels and ships.

"We want the word to get out," says Gary Reed, director of Vessel Traffic Service San Francisco for the U.S. Coast Guard. "We want people to know there are whales in a particular location so they don't encounter them."