Scientists are learning that Google Earth is a good way to verify government activity.

“This shows the promise of Google Earth for collecting and verifying data, which means a few trained scientists can use a freely available program to fact-check governments and other large institutions,” says Jennifer Jacquet, a post-doctoral researcher at the University of British Columbia.

The program they are talking about? Fish.

You see, the Great Wall of China is not the only thing you can see from space. Fish farming cages are clearly visible through Google Earth’s satellite images and University of British Columbia researchers have used them to estimate the amount of fish being cultivated in the Mediterranean.

The study, published today in the online journal PLoS ONE, is the first to estimate seafood production using satellite imagery.

“Our colleagues have repeatedly shown that accurate reporting of wild-caught fish has been a problem, and we wondered whether there might be similar issues for fish farming,” says lead author Pablo Trujillo, an Oceans Science Advisor for Greenpeace International, who conducted the study while a research assistant at the UBC Fisheries Centre.

Almost half the cages were located off the coast of Greece and nearly one-third off of Turkey – and both countries appear to underreport their farmed fish production. The researchers note that not all areas had full satellite coverage – for instance, images were missing for large portions of the coasts of France and Israel, for reasons the authors do not fully understand.

Trujillo adds that Google Earth, with its high-resolution images and consistent time series, can be a powerful tool for scientists and non-governmental organizations to monitor activities related to ocean zoning and capture fisheries.