By Joseph Serna

Los Angeles Times

The California coast is teeming with young sharks, as warming waters and abundant food have created the ideal conditions for feeding, according to experts.

In Southern California, great white sharks have begun to arrive after spending the winter off Baja California. Recently, one of the sharks bit a chunk out of a mother’s leg as she swam off San Onofre State Beach.

The woman, 35-year-old Leanne Ericson of Vista, remains in critical condition and has undergone two of several surgeries scheduled for her injuries, The San Diego Union-Tribune reported.

She lost a lot of blood and was temporarily in an induced coma.

“We are grateful for all of the concern, prayers and good wishes we have received in recent days from the many friends and strangers who have reached out to us from across the country, and indeed, the world,” read a statement from Ericson’s family, released to the Union-Tribune through Scripps Memorial Hospital La Jolla. “The situation could have been far graver had it not been for the number of emergency response personnel and others who provided the care she needed and saved her life.”

Chris Lowe, a biology professor and director of the Shark Lab at California State, Long Beach, said the shark that attacked Ericson on Saturday was likely not a full-grown adult and mistook her for food. Typically, young great whites will feed on fish and rays.

“They have to learn to feed on their own and they’re naive,” Lowe said. “They don’t know how to chase down big prey.”

Adult great whites feed on sea lions and other marine life off islands such as Catalina and San Nicholas, Lowe said. Although it’s not exactly known where the mothers give birth, their babies immediately head toward the shore once they’re born. The sharks are normally off Southern California’s shores between May and October.

But last year, warm waters triggered by El Nino conditions kept the sharks here longer into the winter and drew them back earlier in the spring. Some of the 2- and 3-year-old sharks are here again earlier this year, Lowe said, though he’s not sure why.

“Maybe it just wasn’t cold enough to move those migrations. We just don’t know what’s going on this year,” Lowe said.

But that’s not the only shark mystery this year.

In San Francisco Bay, a huge die-off of leopard sharks and bat rays has sparked concerns among marine life experts.

For weeks now, dead leopard sharks — newborns and mature adults — have been washing up on beaches from San Mateo to Bolinas. Officials with the Pelagic Shark Research Foundation in Monterey believe years of debris, trash and chemical waste pent up in Bay Area storm drains and waterways have finally been washed into the bay because of this winter’s epic storms and are killing the creatures that live there.

Tide gates inside the bay that close during high tide to prevent flooding during a storm can also trap sharks and bat rays in the bay, where they’re then exposed to, and unable to escape, toxic runoff.

“This is an issue of San Francisco Bay sharks and associated wildlife being exposed to toxic watershed … due to Tide Gate entrapment and subsequent discharges into the San Francisco Bay,” the center wrote on Facebook last week.

At the peak of the die-off, dozens of dead sharks were found daily along the coastline, the foundation said. The number of dead sharks has begun to drop in the last week.

In Southern California, however, the shark population is thriving.

On Thursday, Orange County Sheriff’s Sgt. Steve Marble said deputies with the harbor patrol in Dana Point spotted a group of four 6- to 8-foot great whites at the surf line.

Other popular areas for sharks this year include Ventura, Santa Monica and Belmont Shores, Lowe said.

“We’ve learned that these baby white sharks are temperature-sensitive and they don’t like temperatures above 80 degrees. They have this sweet spot, and Southern California is the perfect place from late spring to mid-fall,” Lowe said. “Then Baja becomes the sweet spot.”

Lowe’s researchers recently tracked a 1-year-old shark that stayed around Huntington Beach for 30 days, then moved up to Santa Monica in a matter of hours. It stayed there for a month.