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There’s been a spike in tagged sharks off Southern California this year, but where are they hanging out?

Just when marine scientists think they’ve figured out what great white shark patterns might be off the Southern California coast, the sea creatures change course.

“It’s one of those unusual years, but we don’t know why,” said Chris Lowe, director of the Shark Lab in Long Beach. “That’s the part that is kind of alluring and frustrating at the same time.”

The Shark Lab has been doing aerial surveys from San Diego to Santa Barbara using helicopters and drones to do a census of sharks and attempt to determine if encounter rates can be predictable. (Screengrab video: Patrick Rex/Shark Lab)

Lowe said researchers tagged more sharks than ever this year, a total of 38 so far, a big spike from about a dozen they’ve done in previous years and a sign that their numbers could be growing off Southern California.

When shark sightings surged in 2015 and 2016 along the South Bay, Long Beach, Huntington Beach and San Clemente, there were juveniles that gathered in “hot spot” areas just offshore in those locations, spooking surfers and prompting beach closures.

Scientists believe they were drawn to the area because of the warm water that El Nino conditions brought.

But this year, those once frequented areas have gone cold, with sharks not caring to hang out. Instead, the sharks have been cruising along the coast, using it more like a freeway to pass by to somewhere else.

The Shark Lab, based at Cal State Long Beach, has acoustic trackers along the California coastline that ping tagged sharks as they pass by, allowing researchers to track their locations and analyze their travel patterns.

So where are they going instead?

“We’ve got aggregations of sharks in different places than we’ve had in the past,” Lowe said.

This year, there’s been large numbers of sharks detected off of San Diego, from Imperial Beach to Solana Beach, as well as up in Santa Barbara and even further up the coast in Morro Bay, where the water is typically too cold for the young sharks, which like to bask in the warmer waters close to shore.

In those areas, the sharks are also sticking around longer this year. Typically, they would be gone by this time of year or at least would be starting to leave the area as winter approaches.  It could be they will hang around all winter like they did in those previous El Nino years.

Chris Lowe, director of the Shark Lab at Cal State Long Beach, peers through the jaws of a 4-year old Great White Shark in Long Beach, California, on Monday, June 26, 2017.(Photo by Jeff Gritchen, Orange County Register/SCNG)

“These sharks are picking areas and using those areas for a long period of time,” Lowe said. “There’s something going on we just don’t understand yet.”

The currents and climate might be a clue, or perhaps they create more questions than answers.

“We don’t have all the data, but so far it looks like oceanographic conditions could be impacting that,” Lowe said of the sharks’ migration patterns.

Sea surface temperatures are still lingering in the 70s. The last time that happened this late into the year was the El Nino years of 2015 and 2016.

“Our little bit of data we have so far is that temperature has a lot to do with whether sharks stay all winter or not,” Lowe said. “If our water temperature doesn’t cool down, the sharks that normally leave have no reason to leave. So we’re just going to wait and see.”

This year, there’s a new nursery north of Point Conception, which in the past was “unheard of,” he said.

“To us, that’s a harbinger of climate change,” he said, noting that the water was warmer off Monterey Bay than it has been in years. “That’s a classic sign of species moving north and tracking conditions that are more suitable.”

It’s not just the pups, or five- and six-footers, hanging around this year, but also older juveniles anywhere from 7- to 9-feet in length.

“That’s what leads us to think these hot spot areas are nurseries. There’s plenty of food and the water is warm,” Lowe said. “That very well could be why they are going there.”

Those bigger juveniles have been tracked moving from hot spot to hot spot, quickly darting from areas such as Santa Barbara up to Morro Bay, back to Santa Barbara and then to Santa Cruz, several times in one month, Lowe said.

Some good news if they do stick around local waters: drone footage collected this summer as part of a two-year study shows sharks could really care less, for the most part, about humans swimming and surfing offshore.

A number of long-term factors have helped the shark population rebound, including restrictions on catching the species and protections for their food sources. But with that surge in the great white sharks’ population, researchers are trying to learn more about their behavior to educate ocean users  so the two can co-exist successfully.


Source: Orange County Register

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