Why Are More Sharks Showing Up Offshore in Massachusetts?

Great white shark populations are on the rise, especially in Massachusetts. Last summer a white shark attacked a paddle boarder off the shore. Last week, two Cape Cod beaches shut down after a marine scientist spotted at least one great white shark lurching toward him off the coast. And more recently, a shark took a bite out of a man's leg on Wednesday as he went for a swim.

These encounters are becoming more common as more sharks propagate, drawn to these coastal areas because of the thriving seal populations. These animals are swimming close to the surface of the water, where the seals hang out, and seals can often be seen sunbathing on the rocks off of Cape Cod. Policy installed over the last 30 years to protect these marine mammals, which are a major food source for great whites, could be driving up the shark populations. And, while human encounters with these predators are still extremely rare, they are going up, Gavin Naylor, director of the Florida Program for Shark Research at the Florida Museum of Natural History, told Newsweek.

"We still are talking about probabilities that are tiny," he cautioned. According to the International Shark Attack File, the world's only database of known shark attacks, people have a better chance of being struck by lightning than getting attacked by a shark. The average number of deaths from shark attacks was 26 compared to the 1,970 fatalities from lightning strikes between 1959 and 2010. There have been just four unprovoked shark attacks documented in Massachusetts by the International Shark Attack File.

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Research conducted by the Massachusetts Division of Marine Fisheries revealed that the regional shark population is on the rise since they began their study in 2014.

The scientists search for and count sharks from planes flying near the shore. In 2016, they saw 147 great whites, a significant jump from the 80 documented in 2014.

Greg Skomal, one of the state's top shark experts from the marine fisheries division, said in an interview with the Associated Press last year, that one of the most important findings from the study is the growing number of younger sharks, demonstrating a rise in overall population.

"Last summer [2016], we saw greater numbers of smaller sharks, including juveniles, and that tells us that the population is rebuilding," Skomal said.

Another way marine scientists keep track of sharks is by attaching tags to their bodies. The tags communicate with satellites that alert them of the animal's location, but it only does this when the shark lifts out of the water, usually when feeding on marine mammals. This method of tracking the animals could make it appear like the sharks are mostly in places like the waters off of Massachusetts and California because of the prevalence of seals, Naylor said.

"That estimate is somewhat skewed because we are most likely to find them near the surface," he said. Regardless, it is clear that there is a rise in the numbers of great white sharks, he said.

Some researchers attribute the growth to a cultural shift. The U.S. Marine Mammal Protection Act of 1972 made it illegal to hunt and trade marine mammals, including animals like seals and dolphins.

Before this legislation change, seals had been hunted for their pelts and blubber, decimating the population. Fishermen sometimes harmed these marine mammals in retaliation after the animals stole fish from their underwater nets. Now, with policy in place to protect these creatures, they seem to be thriving and fueling the growth of the shark populations in both California and Massachusetts, Naylor said.

"It is actually quite remarkable how when we put stringent measures in place to regulate fisheries that these animals are pretty resilient and they will recover," he said. "Biology, if you give it half a chance, recovers very well, and this is a great example."