Despite a wealth of local evidence suggesting that world fish stocks are in peril, the United Nations' Food and Agriculture Organization (FAO) has consistently reported that global catch sizes are stable or rising.

But new research suggests that the FAO statistics, which have encouraged investment in the fishing industry, may have been distorted by exaggerated estimates of catch sizes by some countries — particularly China. The reality, say the researchers, is that fish stocks have declined alarmingly over the past decade.

The FAO classifies more than 70% of major marine fisheries as fully or over-exploited. Many populations, such as the North Atlantic cod, have already crashed. But despite these warning signs, FAO statistics for total global fish catches have increased since 1950. These seemingly anomalous figures were put down to the discovery of new stocks.

Reg Watson and Daniel Pauly of the University of British Columbia in Vancouver, Canada, have now reanalysed the FAO statistics, using information about factors such as food abundance and water depth to predict catch levels. They report the results in this issue of Nature (see pages 534–536). Their model mirrored the FAO figures in most regions, but China's reported catches — which account for around 15% of the global harvest — are twice the predicted figure. If Watson and Pauly are correct, and China has over-reported its catches, world fish stocks have actually declined by more than 10% since 1988.

“The results are stunning,” says Jane Lubchenco, a marine biologist at Oregon State University in Corvallis. “We're on a trajectory of significant decline.” Only a drastic overhaul of fishery management can halt the global trend, she says.

Local Chinese officials, whose promotion is linked to their ability to exceed production targets in the country's socialist economy, may be responsible for the over-reporting, believes Pauly. The central Chinese government seemed to acknowledge the problem in 1998, when it placed a cap on the figures reported to the FAO.

Dropping stocks threaten the fishing industry and world food production. Fish provides more than 15% of the world's animal protein, and many developing countries in particular rely heavily on fish catches.