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A spate of shark sightings off the coast of New England in May, including one so dramatic that video caught onlookers screaming, kicked off an earlier season than expected. July is typically when the large predators arrive along the shoreline. And right on cue, as the height of the season arrived, sightings and a flurry of shark bites along New York's Long Island have temporarily shut down beaches and put some East Coast beachgoers on high alert in recent weeks.
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On Wednesday, two people were injured in apparent shark attacks, NBC News reported. According to Suffolk County police, a person was knocked off a paddleboard after suffering a bite from a tiger shark, which resulted in a 4-inch gash to the leg. A few hours later, a person in waist-deep water was bitten on the wrist and buttocks. Neither of the victims' injuries was life-threatening. This is the second time swimming was suspended at Fire Island this month.
Scientists warn that warmer-than-normal waters, along with other factors, may be to blame for more shark encounters along the East Coast this year.
According to OCEARCH, a non-profit data organization that tracks sharks and other marine animals globally, numerous sharks have been spotted off the East Coast this year.
Recent research shows that the weather might influence the shark's behavior more than previously thought.
Joe Merchant, a meteorologist at the National Weather Service in Lubbock, Texas, who has been studying the behavior of great white sharks, specifically off the coast of Cape Cod, Mass., along with marine biologist Greg Skomal, believes there are multiple reasons that shark activity close to the beach has increased. Most of them are environmental factors.
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| Joe Merchant, a meteorologist at the National Weather Service in Lubbock, Texas. Photo courtesy of AccuWeather |
Nearly seven years ago, synchronous with an ongoing marine heat wave, 10 shark attacks were reported off the coast of the Carolinas within a six-week period.
"From June into mid-July, sea surface temperatures there were running about 3 or 4 degrees F higher than normal," Merchant explained in an interview with AccuWeather. "There's some speculation that that led to what is called a cluster of attacks."
The cluster of attacks, coupled with the higher-than-normal sea surface temperatures, made Merchant interested in understanding how the weather might affect the shark's activity.
After looking further into the weather conditions that led up to each of the shark attacks in 2015, Merchant drafted a hypothesis. According to his hypothesis, a sea breeze will set off a predatory chain reaction, increasing the number of sharks near the coast. While not a biologist, Merchant has learned a lot about shark behaviors from Skomal and stands by his hypothesis.
"When the strong dynamic sea breeze mechanism gets going, that enhances upwelling along and near the shoreline," Merchant said in an interview with AccuWeather.
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According to Merchant, the upwelling increases phytoplankton, which affects the entire food chain. The surplus in phytoplankton available to the fish creates a ripple effect, increasing the amount of food available to each level of the food chain, including the sharks. This increase in food increases population numbers.
Merchant explained that the increased amount of bait fish attracts more seals to the shore, and then the great white sharks hunt for the seals.
But Merchant notes that it's not just sea breezes that have brought sharks closer to the shore. Marine heat waves, such as the one off the Carolina coast in 2015, have been linked to increased shark activity.
"An ocean heat wave is a prolonged anomalously warm water event," AccuWeather senior meteorologist Dan Kottlowski said. "[It] is defined as occurring at least five days, and the anomalously warm water values need to be greater than the 90th percentile of the 30-year normal values. Usually, this does not just occur over five days but continues for days and sometimes weeks. In a nutshell: It's abnormally warm water."
"Remember, that's not our environment," Merchant said. "We are stepping into [the shark's] environment. People should be aware of their surroundings."
And sharks aren't the only fans of the higher water temperatures. Humans are more likely to spend more time swimming in warmer water compared to cooler water. This increase in the number of people in the ocean combined with more sharks moving through those warmer waters increases the chance for shark encounters, as Merchant noted, sharks are often lurking nearby.
Sea surface temperatures were above normal along the Northeast coast in early July, but Merchant explained that the departures were not as "extreme" as the 2015 marine heat wave that brought numerous shark attacks to the Carolinas.
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| Areas experiencing a "marine heat wave" as of Sunday. Marine Heat Wave Tracker) |
"The only 'strong' heat wave is occurring offshore of the Virginia capes in the Gulf Stream current. These areas match up with where the most persistent anomalously warm water has been since the spring," Kottlowski said. "These temperatures will continue to rise, and some coastal areas currently designated as 'moderate' will become strong, and some coastal areas not designated as moderate will become moderate. Sea surface temperature values always increase through early September along U.S. coastal areas."
According to Discovery, the great white shark can live in almost all coastal and offshore waters, which have a water temperature between 54 and 75 degrees Fahrenheit. The ideal water temperature for tiger sharks, which are only second to great white sharks in attacking people, is 71.6 F, according to a BBC report.
Since most sharks are cold-blooded, their body temperature matches the temperature of the water surrounding them. Nicholas Payne of Queen's University Belfast and the University of Roehampton recently spoke to BBC about his research on tiger sharks, saying that 22 degrees Celsius is not too hot and not too cold.
"It's about right in terms of their optimal preference for temperature," Payne told BBC in an interview.
An analysis by AccuWeather senior weather editor Jesse Ferrell determined a large section of water off the East Coast was warm enough for sharks in early July.
Water temperatures along Long Island are right around the ideal water temperatures. In Montauk, N.Y., the easternmost point of Long Island, water temperatures reached 70 F on Wednesday, according to the National Weather Service. Water temperatures were just a few degrees warmer, coming in at just 73 degrees F in South Islip, N.Y., which is just a few miles west of Montauk, on Wednesday, according to the NWS.
As water temperatures rise throughout the summer, more areas off the Northeast coast will become habitable for great white sharks.
Merchant warns that as climate change continues to impact coastal waters, higher water temperatures will gradually spread north, which will also increase the sightings and encounters of sharks farther north as well.
Combined with the likelihood for the shark population to expand farther north, the shark population is also increasing, according to Stephen Kajiura, professor of biological sciences at Florida Atlantic University, who shared his thoughts on shark migration habits in a recent AccuWeather Everything Under the Sun podcast.
While the increase in shark population might be alarming or concerning for beachgoers, it is a good thing. Experts say it means the shark population, one that has been on the decline for many years, is finally thriving.
The increase in shark population primarily has to do with an increase in the marine animal populations that the sharks feed on. When a top-level predator population increases, it is a good sign, Kajiura explained, because it indicates a healthy ecosystem.
After years of conservation efforts, the seal population is beginning to increase, and according to a report from Discovery, led to an increase in shark activity in the Northeast this year.
Aerial images and tracking tools, such as OCEARCH, that show just how close sharks lurk to the shoreline may take some by surprise and put beachgoers on high alert.
"There are so many pictures now online from the drones or from the aircraft that show these sharks patrolling," Merchant said. "They are patrolling just feet from the shoreline. People don't realize that there is a 10-foot to 15-foot, if not more, great white shark just swimming around and patrolling out there."
Merchant recommended that beachgoers should not venture in the ocean any farther than waist-depth and should stay in the water for short periods in order to avoid shark encounters and attacks. He also strongly encouraged people to stay out of the ocean at night when a shark sighting is nearly impossible.
