Great white shark numbers are up significantly in Monterey Bay

There is a dramatic increase in the number of great white sharks swimming in Monterey Bay, including an area off Santa Cruz County where a surfer was killed last year, according to a study published Tuesday.

The study found young great whites that are between 5 and 9 feet long and traditionally concentrated in warm waters off northern Mexico and Southern California have moved north since 2014 as water temperatures have warmed.

Where once there were no juvenile white sharks spotted in the ocean between Aptos and Capitola, now there are dozens seen every year, according to research from scientists at the Monterey Bay Aquarium, Duke University and Cal State Long Beach. The sharks swim there in groups between April and October, sometimes within a few yards of the shoreline; some have been photographed swimming near people.

“When the water is warm and they come in the bay, you can see them swim near people all day long. Standup paddlers and kayakers will go right up to them and not realize they are there,” said Chris Gularte, chief pilot with Specialized Helicopters, a tour company in Watsonville that regularly flies over the area.

Last May, surfer Ben Kelly, 26, of Santa Cruz was bitten about 100 yards from shore at Manresa State Beach in Aptos. The bite behind his right knee hit an artery, and he bled to death.

Researchers said such attacks are rare. The influx of young sharks in Northern California, they said, is indicative of broad ocean changes underway because of climate change, affecting many species.

“Monterey Bay is famous for cold water, kelp, otters, anchovies and whales. One thing that hasn’t been here are juvenile white sharks. But in the past five years or so, that has totally changed,” said Kyle S. van Houtan, chief scientist at the Monterey Bay Aquarium.

In Southern California, scientists last year tagged 53 juvenile great white sharks with transmitters, said Chris Lowe, a marine biologist with Cal State Long Beach. He noted that great whites generally avoid people, and when they do bite somebody, it’s often just once.

After they are born, great white sharks stay in warm waters near the shore to feed on fish, rays and squid, said Sal Jorgensen, a marine researcher with UC Santa Cruz and coauthor of the study, which was published in Scientific Reports, a peer-reviewed journal from the publishers of Nature.

After two or three years, the sharks grow to more than 10 feet long and swim out to deeper, colder waters. Their teeth widen and become more serrated. They reach sizes of 17 to 19 feet long and eat sea lions and other marine mammals, often in cold waters in places such as the Farallon Islands off the coast of San Francisco.

The “shark nurseries” where they grow have typically been south of Santa Barbara County. But since the Pacific Ocean off the West Coast warmed considerably in a 2014 event known as “the Blob,” they have moved northward, the scientists found.