A new study says inaccurate reporting of fish catches, particularly by China, has given the false impression that the ocean's fish stocks are plentiful.
Every year since 1950, the U.N. Food and Agriculture Organization has released statistics showing the number of fish in the world. The FAO statistics, compiled from information reported by individual governments, have shown increasing fish stocks - rapidly increasing through the 1960s and more slowly growing since the 1970s.
But world fish catches in many places have been declining, and that discrepancy has puzzled scientists. "One of the seeming paradoxes has been that at a time when most scientists believe that most of the major fisheries in the world have been overfished - and have been overfished for quite a long time - the total catches in the FAO statistics have continued to grow. And that's been something of a puzzle," said Andrew Solow, director of the Marine Policy Center at the Woods Hole Oceanographic Institution in Massachusetts.
Two scientists were troubled enough to conduct their own study. Reg Watson and Daniel Pauly at the University of British Columbia in Vancouver compared the fish catches reported by FAO with expected fish catches, based on sea depth, latitude and other factors. Their results are reported in the journal Nature.
They found that the predicted catches in most areas of the world matched what was reported by FAO. But Mr. Watson says China was a major exception. "It's totally inconsistent with what we get from the rest of the world. We see that we can explain the world's catches over much of the world's surface except for that area, where it appears to be way too high," he explained.
Mr. Watson says for decades China was over-reporting its fish catches. "And they have admitted to the press now that in fact the rationalization that we were given from internal documents is correct, that there has been for a number of years, promotion incentives for middle management people -who are also collecting the statistics - to meet or exaggerate the production targets for their own purposes. These sort of multiplier effects build their way up through the system so when the cumulative total for the whole country is calculated, it gets bigger every year, because each year all these people beat their own production targets of last year. So, you have virtual fish being created," he said.
Then, in 1998, China stopped increasing its production targets. Instead, it has kept them constant, and Mr. Watson says that has resulted in perfectly level Chinese fish catch numbers for the last three years. In either case, he says, it is not accurate. "It is important because with these figures China reports 18 percent of the world's total. So if they exaggerate, it sort of inflates or holds up what would otherwise be a declining global total," he said.
Professor Watson says commercial and conservation decisions are based on the FAO fish catch numbers. For example, he says banks decide whether to finance the construction of new huge fishing trawlers, and fisheries management agencies decide how to regulate fishing in local areas depending on the health and size of the fish stocks there.
Andrew Solow, of the Woods Hole Institution, says most scientists and fisheries managers don't use the FAO numbers because they have long been suspicious of them. But he agrees that an accurate count is important to keep governments from becoming complacent that the fish stocks are plentiful.
"I think there's definitely something in that. To the person on the street - the more naive users of these kinds of statistics - seeing this kind of continuing growth in fish catches might give the impression that there's really no problem, and that scientists or managers who talk about the collapse of the fisheries are being hysterical or overreacting," he said.
Ellen Pikitch, the director of marine programs for the Wildlife Conservation Society in New York, says the FAO numbers are extremely useful, especially for keeping track of the populations of large fish, such as swordfish, tuna or shark, which travel across whole oceans. "One of the ways that I used the statistics was to try to get an understanding of how many sharks were being killed around the world. And the only place to get that all in one place is from the FAO database. It's important to get those numbers right, because if there's any under-reporting or over-reporting, then that impacts whether or not we need to take stronger measures to try to conserve shark populations," she said.
Ms. Pikitch says it now appears that there are more sharks being killed than was thought before, based on the original FAO numbers.
Reg Watson also says the world's fisheries are important beyond the confines of the oceans or as a primary source of human food. He points out that fish meal and fish oils are used extensively in agriculture as animal feed. Therefore, he says an accurate accounting of the global fish stocks is in everyone's interest.
He and his colleague, Daniel Pauly, are now studying additional areas where there has been questionable fish catch reporting. Mr. Watson would not say what countries are under review, but he says they are mostly in Asia.