Deciphering the Attacks

Recent statistics show rise in shark attacks on West Coast

Great white sharks have either been confirmed or strongly suspected in 90 percent of shark attacks on the U.S. West Coast since 1900.

Last week, the Shark Research Committee released their annual report detailing the statistics behind the attacks that occurred along the U.S. West Coast in 2012. According to the report, shark attacks have been on a steady rise over the past decade, with a total of eight attacks occurring on the West Coast last year. The number of attacks in 2012 is six times the average from the 20th century. While this trend in attacks may seem alarming, it should be noted that there were also substantially less people frequenting the ocean along the American West Coast for a large portion of the 20th century.

Dating back nearly 50 years, the Shark Research Committee was founded with the Office of Naval Research, with help from the Smithsonian Institute. According to Ralph Collier, who heads the committee, while the 2012 statistics are indeed indicative of a rise in attacks, they should always be viewed in context.

"If you look at the number of attacks in the American West Coast we've recorded over the 20th century, you'll see that we only noted one attack from 1900 to '49. From 1950 to 2000, we were averaging about two attacks per year, and from 2000 to 2012, we were averaging about three a year," says Collier. "When you increase the number of people in the water, even with a smaller shark population, you're going to see an increase in attacks."

In 2010, there were seven confirmed attacks, and in 2011 there were eight. The victims in the vast majority of recorded attacks have been surfers; since 2000, they’ve made up 67 percent of attacks. Great white sharks have either been confirmed or strongly suspected in nearly 90 percent of attacks since 1900.

Collier cites population dynamics as the fundamental reason for the rise in attacks in recent history. "If you couple the increased amount of people in the water along with the rise of the seal population, that helps explain some of it." As Collier referenced, in 1972, under the Marine Mammal Protection Act, it became illegal to kill seals in the United States.

Alarmingly, according to the Shark Research Committee, the majority of all attacks seem to occur in a three-month window spanning from August to October. Since 2000, 49 percent of all attacks on the West Coast have occurred in this window. Collier says there a few different theories to account for the attacks that occur during the fall. One is a potential connection with salmon and steelhead making their way downstream when rivermouths burst into the ocean, often times creating good sandbars and feeding grounds. This period also lines up with when many seal pups, who are easy prey, are born. "To be honest,” says Collier, “I'm almost surprised there aren't actually more attacks."