Bus-sized Basking Sharks Return to California Waters After 30-year Absence

basking sharks
Basking sharks at an aquarium in Tenerife, Canary Islands, Spain, 2007. Peter Thompson/Heritage Images/Getty Images

Basking sharks could be returning to California waters after a 30-year period in which they have barely been seen by human eyes in the region.

Usually, sightings of these gentle giants—which are the second-largest living sharks—off the California coast are extremely rare, but two have occurred over the course of the last month.

"It was a very special thing," Captain Skip Rutzick, who is in charge of The Duchess Yacht Charter Service in Marina del Rey, told local magazine The Argonaut. "I've been on the ocean 1,000 times in the last five years and I've seen many whales, I couldn't tell you how many thousands of dolphins, and the very rare ocean sunfish the Mola mola—but to see a basking shark was very special."

The two sightings took place in almost exactly the same location—around three to four miles off the south-facing Malibu coast—on March 31 and April 20. Both incidents were caught on camera by the crews of the vessels involved.

In order to confirm that the animals were indeed basking sharks, the images were shown to underwater photographer and marine life expert Brad Wilbourn. Based on their behavior and the size of their body parts, he suggested that both were basking sharks measuring between 20 and 25 feet.

"They were moving very, very slow," Wilbourn told The Argonaut. "Basking sharks are very slow and lumbering, and they really take their time because they're filter feeders—their mouth is wide open and they're gathering whatever plankton they can get ahold of."

In the early 20th century, basking sharks used to congregate in their hundreds, or even thousands, to feed on plankton off the California coast.

But in the 1960s their numbers here took a nosedive as a result of targeted fishing and eradication programs, to the extent that they were listed as a "Species of Concern" in the eastern North Pacific. That is according to the National Oceanic and Atmospheric Administration.

Now, experts are hopeful that the sightings over the last month—just two of several encounters that have been reported with the sharks in recent times around the Channel Islands—mark a return of the animal to California waters.

"I hope it's a sign of comeback," Heidi Dewar, a NOAA fisheries research biologist, told The Ventura County Star. "But given the variability in sightings, I think we have to wait a few more years before we can say that with confidence."

Christopher Lowe, director of the California State University's Shark Lab, said: "It has really been 30 years since we've seen them in any numbers."

The animals—the largest of which can grow up to 33 feet in length, or around the size of a bus—are one of three plankton-eating shark species. They feed with their mouths wide open to suck in as much plankton as possible. Despite their size, we know very little about them, although they are generally considered harmless to humans.