Do Attacking Sharks Really Surface Their Fins?

Slate's Culture Blog
July 11 2012 3:40 PM

Do Attacking Sharks Really Surface Their Fins?

A photo of a shark trailing a novice kayaker has attracted Jaws comparisons all over the internet, as it shows a menacing dorsal fin slicing through the water just behind the frightened kayaker. Do great whites and others sharks really surface their fins while pursuing tasty humans?

Yes, but a man-eater would probably attack you from underneath. “Surface finning is common behavior in several shark species,” according to marine biologist Carl Meyer, who has published several papers on the movement patterns of sharks. Meyer told me that “white sharks routinely investigate objects on the surface” and “following kayakers is not uncommon for this species or other large sharks (e.g. tiger sharks).” However, usually the shark is only checking the kayaker out, not hunting him down, and these pursuits “rarely result in the shark biting the kayak.” White sharks do snatch some prey from the surface, such as seals, but usually do so by “ambushing them from underneath,” as in this video from Planet Earth.

Great whites swim in a variety of patterns from surface to seabed, including “yo-yo swimming” (repeated dives and climbs from bottom to top), swimming along the ocean floor, “spike dives” (often around dawn and dusk), and surface swimming, so in the less deep waters along the coast you could find them at any depth. In the open ocean, on the other hand, they may swim on the surface or several hundred meters deep, sometimes diving as deep as 1000 meters.

Photo of shark fin

Photo of a shark fin from Wikimedia Commons.

As Meyer reminds us, “it is extremely unusual for white sharks to bite people” and “only a handful of confirmed white shark attacks on humans occur each year worldwide.” Last year the University of Florida reported 75 shark attacks around the world, resulting in an unusually high 12 deaths (though none of these were in the United States). Between 2001 and 2010 the average number of fatalities from shark attacks worldwide was only 4.3.

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And it turns out that the shark that chased the Cape Cod kayaker was probably not a great white, but instead just a harmless basking shark. Shark expert Greg Skomal of the Massachusetts Division of Marine Fisheries told the Associated Press that based on the shape of the fin “he’s almost positive it was a basking shark,” a giant fish that only eats plankton. Meyer agreed.

Of course, if you see a sinister-looking dorsal fin cut through the water, there’s one last possibility: It could be a shark boy.

Previously

Stop Calling Them Shark "Attacks"

Forrest Wickman is a Slate staff writer.