The world's fishing industry has taken twice as much fish from the globe's oceans in the last 60 years than has been officially reported, a new study says.

Numbers reported to the United Nation's Food and Agriculture Organization, which tracks statistics on fishing worldwide, are tens of millions of tons less than what is actually being taken, say fisheries researchers Daniel Pauly and Dirk Zeller of the University of British Columbia.

That's because countries generally report numbers from industrial-scale fishing but routinely miss important data on fishing activities on a smaller scale, including subsistence, artisanal and illegal fishing as well as discarded by-catch, they say.

"The world is withdrawing from a joint bank account of fish without knowing what has been withdrawn or the remaining balance," says study leader author Pauly, who is part of the university's Sea Around Us research initiative.

Ongoing declines in global fishing catches are accelerating as stocks are being exhausted, say the researchers who've used "catch reconstruction" including estimates of the unreported fishing activities in an effort to more accurately gauge the impact on fishing around the globe.

Accurate data is important in formulating fishing policies such as catch quotas and seasonal or geographical restrictions, they say.

"Better estimating the amount we're taking out can help ensure there is enough fish to sustain us in the future," says Pauly.

Their reconstruction shows that globally, 53 percent more fish were taken from oceans than official figures suggest, the researchers report in the journal Nature Communication.

They say their estimates of the global catch in just one year, 2010, was 109 million tons, around 30 percent greater than the official report of 77 million tons reported to the U.N.'s FAO by more than 200 countries around the world.

Every year, they estimate, fish that are caught but go unreported total around 32 tons, more than the weight of the entire human population of the United States.

Pauly and Zeller note that their estimates suggest global fisheries catches have been declining significantly since hitting a peak of 130 millions tons in 1996.

That contradicts FAO data, which indicates a catch of 86 million tons in 1996 and only slight declines since then.

Pauly stands by his assertion of significant declines, which he says is due at least partially to collapses of some global fish stocks.

Although FAO data has long been the only available estimates of annual global fish catch, "the FAO doesn't have a mandate to correct the data they get," Pauly says, and is at the mercy of the member countries and the data they submit.

The FAO, in a statement, says it welcomes the new study, and agrees that "catch statistics (including estimates of additional sources of removals) can and should be improved, and this requires additional funding and international collaboration and country commitment."

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