Humans, mainly those in countries with a craving for shark-fin soup, have devoured so many of the oceans’ top predators that it has rattled the length of the marine food chain, according to a study to be published today in the prestigious journal Science. While previous studies have calculated declines by half or more, this one argues that seven of the largest sharks along the Atlantic Coast have all but vanished because of overfishing — down as much as 99 percent for bull, dusky and smooth hammerheads over the last 35 years.
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The study’s premise: As larger sharks disappeared, smaller ones and rays, both often prey, exploded over the same period. One in particular, the cownose ray, perpetuated to the point that by 2004 it gulped down much of the scallop population in Chesapeake Bay. ”I think that’s just the tip of an iceberg,” Fordham said. “There are so many connections we don’t understand. Sharks keep the oceans in balance.”