The fishing industry has responded by waging an all-out war on sharks. Since the fins are so valuable, fishermen haul sharks on board, slice off the fins, and throw the sharks overboard to bleed to death, like poachers kill rhinoceroses just to take their horns. Up to 70 million sharks die this ignominious death every year, carnage equally inhumane and ecologically unsustainable. And because it's extremely difficult to identify a shark species by the fins alone, fishermen get away with slaughtering the most vulnerable sharks, from the fearsome great white shark to the harmless filter-feeding basking shark.
Big predator fish like sharks have suffered huge losses from fishing since the 1950s, when the commercial fleet became fully mechanized after World War II. But just as with the depleted populations of sea turtles brought to light by Jeremy Jackson only in the late 1990s, we've been late to notice sharks' dwindling numbers. As late as 1954, two top academics published a book called The Inexhaustible Sea that echoed Huxley's perennial optimism that the oceans were simply too large for humanity to ever empty of life. And yet the late Ransom Myers and his colleague Boris Worm showed in a landmark study in 2003 that many big predator fish--like tuna, swordfish, marlin, cod, flounder, and halibut--had been reduced to less than 10 percent of their 1950 numbers. And as we've seen, by 1950, many of those fish had already been suffering from intense fishing pressure for some time.
One reason we didn't notice the world's failing fisheries was because it was disguised for years in the official data. If you looked at United Nations figures for global fish catch in the 1990s, it showed a steady increase every year for the entirety of its data set. But Daniel Pauly and Reg Watson, fisheries scientists at the University of British Columbia, were skeptical. China, one of the world's behemoths when it comes to seafood consumption, was consistently reporting jumps in catch every year since the 1980s--a claim that flew in the face of on-the-water reports of diminishing catches. So Pauly and Watson redid the data in 2001, correcting China's overinflated claims and accounting for vast natural fluctuations in the world's biggest fisheries in South America. With the data corrected, the statistics suddenly showed a different story: Global fish catch was not rising. It wasn't even holding steady. Instead, it had peaked in the late 1980s at about 90 million tons and has been in jagged decline ever since, even though we were searching for the most obscure fish in the deepest recesses of the oceans with megaships like the Atlantic Dawn.
There's another reason we haven't noticed the creeping desertification of the once-vibrant seas. We simply fail to remember. Pauly coined the term shifting baseline syndrome in 1995 to describe our collective amnesia when it comes to what constitutes healthy oceans. It's a syndrome with a long pedigree. John Smith, accustomed to the smaller fish common in England's North Sea as a result of centuries of overfishing, showed it with his amazement at the massive codfish abundant in New England's healthy waters.
The concept of shifting baselines was adeptly demonstrated by a doctoral student's project in 2009. Loren McClenachan from the University of California's Scripps Institution of Oceanography pored over hundreds of photos of trophy fish caught in Key West over the last half century. The photographs showed the biggest catches of the day, like groupers, sharks, and sawfish, hung on a wooden dockside rack. In the 1950s photos, huge fish competed for space on the rack, draped one over another. By the 1980s, the fish were small enough to be displayed in nicely contained rows. And by the 2000s, the trophy fish of the day were barely bigger than what you might find in a well-stocked koi pond. Yet today's recreational fishers tacking their best catches to the board and posing for pictures feel just as proud as their predecessors.