Great whites abandoned San Diego nursery, but El Niño could bring sharks that 'play by different rules'

SAN DIEGO — Given that great white sharks are mostly uninterested in humans, San Diego beachgoers are never likely to have an encounter with one of the predators. But experts said that could be even more true this year, now that a once-active nursery has apparently fallen out of favor with the juvenile great whites that spent several recent summers here. At least for now.

“San Diego County … had a nursery between Del Mar and Torrey Pines that persisted for about four years, and then last year all the sharks left,” Chris Lowe, the director of Cal State Long Beach’s Shark Lab, said in an interview. “We’ve got people flying (drones) there, we’ve got acoustic receivers to detect tagged ones … but we just haven’t detected any down there for about a year.”

Why that is, researchers don’t know with certainty, though Lowe’s leading theory is that the sharks depleted their favorite prey and moved on to coastal waters farther north with a more plentiful food supply. Whatever the case, Lowe expects that while Orange and Los Angeles counties could experience a “sharky summer” this year, juvenile great whites should remain a rare sighting in 2026 in San Diego, at least through the early and middle parts of the summer.

However, with some experts predicting an unusually strong El Niño this year, the warm water that would accompany such a system could bring different species north from Mexico, Lowe said. That could include tiger, bull and hammerhead sharks, which is what happened during the last particularly strong El Niño in 2015. That summer, there were two reported hammerhead attacks in California, and officials briefly closed beaches in La Jolla following the sighting of a hammerhead that was reportedly behaving aggressively.

“Having white sharks off your beach really isn’t that much of a concern, because we’ve had it for years and (there are) very few bites,” Lowe said. “But when those other species come up, they play by different rules, and we don’t know enough about their behavior yet.”

‘Great white hype’

For those San Diego beachgoers rejoicing over the current lack of detectable great whites, there really isn’t much to celebrate, according to shark experts.

“White sharks are top ocean predators that deserve respect; however, juvenile white sharks in Southern California are generally not interested in humans,” said Jack Elstner, a shark researcher and doctoral student at UC San Diego’s Scripps Institution of Oceanography. “They are a natural part of a healthy ecosystem.”

Lowe said the perception of great whites as a particularly dangerous and aggressive species is wrong, and that they generally “treat people like flotsam” and leave them alone.

“Their reputation precedes them, but it’s unwarranted,” Lowe said. “The ‘great white hype’ is what we call it … We have lots of drone footage of them just swimming right under these surfers and swimmers like they’re not even there.”

Lowe and his team at the Shark Lab, along with Elstner and other researchers who work with the group, study white shark populations between the Mexican border and Monterey, a stretch of roughly 450 miles. Within that area, there are currently about 240 sharks the team has tagged with acoustic transmitters.

Researchers say most white sharks head south for the winter in search of warmer water, then return to California’s waters as temperatures rise. The white sharks that frequent the California coastline are mostly juveniles that range in size from 4½ to 10 feet long, according to Lowe. While larger adult sharks sometimes come closer to shore to feed on seals or give birth, it’s the juveniles that prefer aggregating close to shore where water temperatures are mild, there is plentiful prey and there are fewer predators.

“At this stage of their lives, juveniles are pretty temperature sensitive,” Elstner said. “They don’t like it way too hot or way too cold; they want it just right.”

Lowe also said water temperature is the No. 1 influence on where juvenile white sharks choose to aggregate, but he and other experts are continuing to study other reasons why certain coastal areas fall in and out of favor with the animals.

The Shark Lab conducted a diet study that used both baited underwater cameras and water samples to study the differences between juvenile aggregation sites and non-aggregation sites. In Del Mar, which was one of the aggregation sites at the time of the study, the scientists found less of the foods sharks seem to prefer, such as halibut, smaller sharks and their favorite meal, stingrays, which researchers jokingly call “shark pancakes,” Lowe said.

“What we think happens is the white shark aggregations feed those things down … and eventually it gets too hard to find their favorite food, so the sharks leave,” Lowe said.

So far this year, the Shark Lab is tracking aggregation sites that appear to be forming in waters near Santa Barbara and Santa Monica, but none in San Diego County. On Wednesday morning, Lowe headed out on the water to try to tag individuals from an aggregation of about 15 “very small juvenile white sharks” near Redondo Beach.

Repeat of ‘epic’ 2015?

There remains uncertainty about whether an El Niño system will form this year, and if it does, just how strong it will be, but the National Oceanic and Atmospheric Administration says there is a 25% chance of a very strong El Niño late this year.

If that happens, Lowe expects similar results to 2015, when a record-breaking El Niño caused ocean temperatures in the eastern Pacific to spike.

“There were sharks everywhere,” Lowe said, recounting sightings that occurred in the Long Beach Harbor and other unexpected places. “That was an epic year.”

Included in those sightings were species of sharks, such as hammerheads, that typically stick to the warmer waters south of Baja California but were able to venture north amid the ocean heatwave.

In late August 2015, a hammerhead that was reportedly behaving aggressively prompted beach closures in La Jolla. That same summer, a spearfisherman was attacked by a hammerhead off Santa Cruz Island, and a kayaking fisherman was bit by a hammerhead near Malibu.

“Hammerheads get really excited around wounded fish and fish blood … and they’re not afraid to come right up to a boat,” Lowe said. “So we always warn fishers, and especially spearfishers who are in the water, you definitely have to keep your eyes open because they will get jazzed up around dead fish.”

Lowe said strong El Niño systems and their warm waters can also bring to California other fish species and ocean creatures that typically prefer tropical and sub-tropical waters, including mahi mahi, tuna crabs, whale sharks and manta rays.

“That is definitely not usual,” Lowe said.

Lowe and Elstner said the long-term impacts of a strong El Niño are harder to predict, but both said that’s what makes their research, which contributes to public safety and decisions to close beaches when sharks are sighted, so important.

Elstner said it’s also important to keep in mind that nursery aggregation “hot spots” can be dynamic.

“Just because there are not white sharks in San Diego now,” he said, “that doesn’t mean they won’t be here later on.”