Plenty of fish in the sea? Maybe not

The global fisheries catch has been underestimated by more than half since 1950, with tens of millions of tonnes unreported every year, said a study Tuesday, warning that stocks may be running low.

About 109 million tonnes of fish were caught in 2010 -- 30 percent higher than the 77 million tonnes reported to the UN's Food and Agriculture Organization (FAO), according to the study.

This meant that about 32 million tonnes of catch went unreported that year, "more than the weight of the entire population of the United States," said a research duo from the University of British Columbia, Canada.

In the peak fishing year of 1996, the FAO had documented a global catch of 86 million tonnes. In fact, it was closer to 130 million tonnes, according to the research published in Nature Communications.

"The world is withdrawing from a joint bank account of fish without knowing what has been withdrawn, or the remaining balance," said the study's lead author Daniel Pauly.

For the study, Pauly and his colleague Dirk Zeller compiled a "catch reconstruction", combining FAO data with estimates of figures countries generally excluded from their official reports.

These included small-scale commercial or subsistence fishing, recreational or illegal fishing, and discarded bycatch.

The pair of researchers, backed by a team of 100 collaborators from more than 50 institutions, relied on academic literature, industrial fishing statistics, local fisheries experts, law enforcers, coastal communities and tourist catch data.

"We find that reconstructed global catches between 1950 and 2010 were 50 percent higher than data reported to FAO suggest," the authors wrote.

They called for more robust reporting and monitoring of catches. 

"This groundbreaking study confirms that we are taking far more fish from our oceans than the official data suggests," commented Joshua Reichert, vice president of the Pew Charitable Trusts, which supported the work.

"It's no longer acceptable to mark down artisanal, subsistence or bycatch catch data as zero in the official record books."