We know that there are very few fish in the ocean. But there may be even less fish in the world’s oceans than we thought, creating a serious problem for communities that rely on seafood for daily calories.

That’s according to new research showing that global catches were up to 50% higher between 1950 to 2010 than official United Nations figures. The Food and Agriculture Organization (FAO) had said catches peaked at 94 (U.S.) tons in 1996, before declining thereafter. New estimates, which cover a wide range of fishing activity, say catches were already as high as 143 million tons by that time.

“The world is withdrawing from a joint bank account of fish without knowing what has been withdrawn or the remaining balance,” says Daniel Pauly, a professor at the University of British Columbia and lead author of the study. “Better estimating of the amount we’re taking out can help ensure there is enough fish to sustain us in the future.”

Unlike official estimates, Pauly’s numbers include data from small-scale fisheries, recreational fishing, illegal fishing, and fish caught and then discarded. The research, which is 10 years in the making, is based on input from 400 researchers around the world. In 2010, the gap between official figures and the “reconstructed” ones in the study was 30%. About 35 million tons of caught fish failed to be recognized by the FAO, the study says.

Up to 1 billion people worldwide rely on seafood as their main form of protein, so understanding exactly what’s left in the oceans is no trifling matter. “The differing trajectories documented here suggest a need for improved monitoring of all fisheries, including often neglected small-scale fisheries, and illegal and other problematic fisheries, as well as discarded by-catch,” the study, published in the journal Nature, says.