Researchers this week revealed that they may have found overfishing using images from Google Earth.

The study, published in the ICES Journal of Marine Science, shows that some fishing weirs located in the Persian Gulf are much larger than they are supposed to be. Fishing wiers are large traps that use tides to catch fish not far from shore.

“This ancient fishing technique has been around for thousands of years,” said Dalal Al-Abdulrazzak, lead author of the study and a PhD student at the University of British Columbia. “But we haven’t been able to truly grasp their impact on our marine resources until now, with the help of modern technology.”

These traps, according to the study, could be catching up to six times the amount of fish that their host countries have reported officially to the United Nation’s Food and Agriculture Organization. Researchers looked at 1,900 Persian Gulf fishing weirs using data from Google Earth and estimate that around 31,000 tonnes of fish were caught by the traps during 2005. This is far more than the 5,360 tonnes reported to the UN for that year by the seven countries the weirs are located in.

“Time and again we’ve seen that global fisheries catch data don’t add up,” said Daniel Pauly, a co-author of the study. “Because countries don’t provide reliable information on their fisheries’ catches, we need to expand our thinking and look at other sources of information and new technologies to tell us about what’s happening in our oceans.”