Dr. Chris Lowe, director of the Cal State Long Beach Shark Lab, attributes the increase in sharks, specifically great whites, to a multitude of factors. He suspects sharks are beginning to see the fruits of 20 years of federal protection, following 50 years in which the predator was "systematically eliminated from our coastal waters."
Protections apply to the full spectrum of marine mammals, whose "populations have come back better than anyone could have predicted," said Lowe. Mature great whites feed on marine mammals such as otters, sea lions and seals, and the increase in prey could contribute to growth of the predator population.
"The number of seals, sea lions and otters that have been observed with white shark bites have been steadily increasing since 2002," Lowe said.
Such data fails to address a question on many Orange County residents' minds: Why are great whites choosing to congregate in Southern California? And why now?
Great whites typically summer in the 60-degree waters of Southern California before heading southward to Baja California as the changing of the season leads to colder temperatures. But that changed during the El Niño event from 2014-2016.
"During El Niño, we didn't have winter and our water temperatures didn't drop below 60 degrees," said Lowe. "The sharks stayed."
The bewildering trend has continued in recent years, even without the warmer temperatures of El Niño. This year, says Lowe, researchers observed sharks sticking around Southern California for most of the winter.
"We haven't quite figured this out yet," said Lowe, who theorizes that the warm waters — a result of global climate change — and the overall increase in shark numbers contribute to what he calls "hotspots," or beaches where sharks have been observed in larger packs. Those beaches include Huntington Beach, San Onofre, Santa Monica Bay, and Ventura.
While scientists are uncertain why specific beaches have become hotspots, they are able to track trends in behavior. Most of the sharks that swim close to the shore — and are likely responsible for attacks — are juveniles.
Upon birth, baby sharks must fend for themselves. Waters 100 to 200 feet from the shore are safer, as predators rarely stray into shallow water. Also, easy-to-catch shark prey, like stingrays, are abundant. These are the same waters where swimmers and surfers tread.
Scientists don't know what causes a shark to attack, but it could be self-defense or a case of mistaken identity, in which sharks perceive swimmers as prey.