An airborne white shark chasing a seal in 2010.Photo: CARL DE SOUZA/AFP (Getty Images)
If you visited the Ocearch marine animal tracker in the last week, your eyes might have been drawn to the eastern seaboard of North America, where a bombardment of blue dots made it look like the coastline was being assaulted by white sharks.
Panicky tweets ensued along with typically hyperbolic tabloid headlines, but it turns out the amalgam of elasmobranches is nothing to worry about. It’s just shark migration season along the coast, though climate change could be playing a longer term role.
“These headlines come up just about every time somebody goes on the shark tracker and just has a display, all the tags,” Charles Bangley, a marine ecologist at Dalhousie University, said. “There probably always have been more sharks than you would have expected. It’s just that we have the technology now to actually see them.”
Eighty-three tagged white sharks are currently seeing out their migration from the cooling waters off Massachusetts and Canada to the warmer havens of North Carolina and Florida. Sharks head out at different times, meaning the animals are spread along the coast. Bangley said that climate change is affecting those migrations, as the animals will head out of the northern waters later in the year than normal, as the water temperatures stay balmier for longer.
“One of the reasons you see this big spread right now is that those sharks are still kind of transiting,” Bangley said. “So you have some sharks that could have already made it all the way down to Florida, and then you have the sharks that are just now getting around to leaving Nova Scotia waters.”
Warmer temperatures will also get the sharks to stay closer to shore, Bangley said, a phenomenon that can increase the number of shark sightings. (Shark attacks on humans remain an extremely rare occurrence, but the animals’ proximity means sightings are relatively common.)
All told, the number of sharks on the tracker is actually a testament to the success of white shark conservation efforts, according to Bangley. An animal once demonized (perhaps most famously by the film Jaws) is no longer being hounded by humankind. “These shark populations are recovering back to what had been their natural levels before they were overfished,” Bangley said. “It seems like way more sharks because a generation of fishermen have grown up with depleted shark populations, but it’s actually almost like the system is going back to normal.”
Of course, the world recovering shark populations are returning to is a very different one than has existed before. Climate change is changing the color of the oceans, melting Arctic ice, and reducing the oxygen in the water.
Sharks themselves have found some way to adapt, including spending more time further north as waters heat up. But rising temperatures are also putting pressure on some species, to say nothing of the impacts of industrial fishing. Overall, an estimated 70% of sharks have been wiped out over the past 50 years alone. So even if the current shark migration is normal, perhaps we shouldn’t be surprised if the sharks do decide to amass and rise up one day soon.
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