Unusual Warm Sea, Sharks & Otters


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Mike Harris, a sea otter biologist with the California Department of Fish and Wildlife who works out of Morro Bay, has been noticing a trend for about 10 years now: Great white sharks love to chomp sea otters.

BY TRAVIS GIBSON
tgibson@thetribunenews.com

–From The  Tribune, San Luis Obispo

If it seems that there have been more large shark sightings on the Central Coast than usual for this time of year, that’s because there have been.

Last week was dubbed Central Coast Shark Week by some after a number of sightings in the waters off San Luis Obispo County.

It started when Cal Poly student Brad Beekman captured photos and video of a large shark swimming near surfers near Cayucos on the Fourth of July. Another credible sighting was reported at Morro Strand State Beach the next morning. The sightings, believed to be of the same shark, prompted State Parks officials to post warning signs.

Then the Pismo Beach Pier became a hot spot, drawing controversy along the way.

Two great white pups, about 4 to 5 feet long, have been caught in the past month from the pier, one possibly illegally. Then, a 10- to 12-foot white shark swimming near the pier was seen on two different videos last weekend.

So the question is: Why have there been so many sightings outside late summer and early fall, the typical peak season for sharks?

The popular theory is that unseasonably warmer water has brought the change, but experts say it is much more complex than that.

If El Niño is the Spanish-speaking child star of weather events, the Blob is its ugly stepbrother who placed fifth in the spelling bee.

Much of the talk in the news last year and into this year focused on El Niño, a weather pattern that sends tropical water from the western Pacific across the equator, often bringing increased rain and ocean temperatures to the California coast. Though El Niño had plenty of effects on California last year, eroding beaches with massive waves, the effects of the Blob were already prevalent before it showed up.

Nicknamed the Blob by University of Washington researchers, this high-pressure weather system developed in fall 2013 off the Pacific Northwest, causing fewer and weaker storms to drive down the West Coast from Alaska. The result was fewer storms to churn ocean waters and cause upwelling of deep, colder nutrient-rich seawater. Instead, stagnant warm water hung off the California coast. Then came El Niño’s tropical influence.

Combined, El Niño and the Blob have had a wide-reaching impact on all marine life, including sharks.

“We had a strange sequence of events last year,” Elliott Hazen, a National Oceanic and Atmospheric Administration biologist, said last week. “It looked like an El Niño, but it kinda stopped. Instead we got the Blob, which was much more important.”

New research by NOAA indicates that the Blob, which Hazen compared to a warm bowl of water with no circulation, combined with a weakened El Niño to strongly depress the productivity of the marine ecosystem off the West Coast, with the Blob driving most of the impact. Warm waters slowed the flow of nutrients from the deep ocean and reduced the productivity of coastal ecosystems, according to a paper Hazen co-authored.

Ralph Collier, a marine biologist for more than 50 years and founder of the Shark Research Committee, said the increase in water temperatures — up to 5 degrees above average off the coast of Central California — in the past few years has led to more great white sharks heading north from their usual early summer hunting areas in Southern California.

“What we are looking at is a domino effect,” Collier said. “The bottom of the food chain is moving north, so animals that feed on them are moving too.”

The warm waters off the Central California coast have affected the entire ecosystem.

Hazen said humpback whales have been moving closer to shore, tropical pelagic red crabs have washed up on Central Coast beaches and more sport fish are showing up along Southern California.

White sharks 2 years old or younger, like the ones caught off the Pismo Beach Pier recently, are no longer confined to the warmer waters off Southern California, where they usually grow quickly and expend less energy warming their bodies, Collier said.

Collier said the effects of the Blob and El Niño are dissipating, but it’s unclear what the future holds. June was Earth’s 14th straight record-hot month and the trend is expected to continue.

Sea otter, shark correlation

In addition to the warm waters off the coast, something else seems to be a factor in the increasing shark population.

Mike Harris, a sea otter biologist with the California Department of Fish and Wildlife who works out of Morro Bay, has been noticing a trend for about 10 years now: Great white sharks love to chomp sea otters.

Out of the 30 sea otter carcasses recovered along the California coast during the first two weeks of July, 14 showed evidence of a shark bite, Harris said.

Sharks don’t feed on otters, and scientists say there has never been a sea otter found in the stomach of a great white. Harris, who has teamed up with Collier to investigate the abnormal behavior, said that while they are not sure why sharks keep biting sea otters, the number of bites has been used to monitor shark activity.

“We started noticing a significant change (in shark-bitten sea otters) … and it has continued to increase,” Harris said. “To me, that’s an indication that there are more sharks in the area.”

Harris said a healthy local population of elephant seals and sea lions, the white shark’s main prey, is one possible reason for the increase. Harris said he also believes that conservation efforts, including the law passed by California in 1994 making it illegal to target great white sharks while fishing, are finally taking hold.

“A lot of the things that used to eliminate sharks from the area, gillnetting for example, have essentially been eliminated through much of this area, so we no longer have loss of white shark population,” Harris said.

It has been historically difficult to track great white shark populations, so no published research exists to support Harris’ take, but Collier agrees.

“I don’t know how much (the shark population) has grown,” Collier said. “It is just a personal observation. Population has gone up.”

And according to Harris’ observations, not only are there more sharks on the Central Coast these days, but they are sticking around longer.

“The adults are known to come to the Central California coastline summer into fall and then leave. We were telling (shark researchers) we are seeing shark-bitten otters throughout the year, but our peak is then. Now what we are seeing is instead of having a real prominent peak, it’s quite spread,” Harris said. “Last year we were getting a large amount of shark-bitten otters into February and March.”

As global temperatures continue to hit record highs and shark conservation efforts take hold, it’s safe to say that shark activity won’t slow down anytime soon. So what now?

Sarah Beardmore was about to go surfing a couple years ago near her home in Australia when she saw people rushing to get out of the water. Someone had spotted a shark.

“No one was doing anything,” Beardmore, a former pro surfer, said in a phone interview from Australia. “Later that afternoon, I came back and people were still going into the water. No one knew there was a shark spotted. That’s when I knew I wanted to do something.”

Beardmore teamed up with Allan Bennetto, who had the idea for Dorsal, a crowdsourced shark-spotting app that launched in October. Bennetto created the app after a shark attack killed a Tasmanian diver who was unaware he was swimming in an area where a shark was seen the day before. The goal of the app, and http://www.DorsalWatch.com, is to allow surfers and beach-goers who see a shark to report the sighting, using geolocation, where it can be quickly viewed by anyone with a smartphone or computer. Beardmore and Bennetto launched the app in the United States in June.

The app has grown quickly in Australia — where there have been five unprovoked shark attacks this year, including two deaths in June — and now has more than 200,000 daily users, Beardmore said.

“In most cases, reports come out a day later,” Beardmore said. “The app is just about being aware and keeping the public informed.”

But Collier, the marine biologist, said apps and live shark-tracking devices, such as ones used by OCEARCH, aren’t all positive. He said that shark locators make work easier for shark poachers, and reporting apps set up the increased potential for surfers tired of crowded waves to call in false reports.

“If everyone were honest, that technology would be great,” Collier said. “Unfortunately, that isn’t the case.”

But Beardmore said feedback from others in the scientific community has been supportive and added the app has the secondary benefit of helping to determine shark behavior patterns. In order to combat fraudulent reports, Beardmore and a small team of volunteers work to verify each report using a six-step process.

Safety efforts have ramped up following a record 98 unprovoked attacks worldwide in 2015. In May, a woman swimming off the coast of Corona del Mar State Beach was attacked by a great white.

Collier said shark safety is all about awareness.

“We found that most bites were taking place in Central California and Northern California in August, September and October,” Collier said. “We started looking into those locations, and the majority, over 80 percent, happened near river mouths when salmon spawning was taking place.”

The seals came for the salmon, the sharks came for the seals, then we got in the way, Collier said.

Still, studies show the average beachgoer shouldn’t get freaked out by the threat of sharks.

A Stanford study last year found that the risk of being attacked by a shark off the California coast has dropped by more than 91 percent since 1950. Oceangoers are 1,817 times more likely to drown than die from a shark attack, and surfers have just a 1-in-17 million chance of being bitten, according to the study.

“You have a better chance of cutting your foot on a glass bottle walking on the beach than being bitten by a shark,” Collier said.

Travis Gibson: 805-781-7993, tgibson@thetribunenews.com, @TravisDgibson

 



Categories: El Nino, Great White Sharks, Warming Oceans

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