University of British Colombia scientists used Google Earth satellite images to assess fishing practices in the Persian Gulf, reporting that large fish traps known as weirs could be catching up to six times as many fish as are being reported.

The UBC researchers estimated that there were 1,900 fishing weirs along the coast of the Persian Gulf, noting that for that year - 2005 - official fish take numbers from seven countries were reported to be 5,260 metric tons.

With that many weirs, the researchers contend the actual fish take was more like 31,000 metric tons, which represents a difference of more than 25,000 metric tons, about twice the weight of the Eiffel Tower.

Fishing weirs are semi-permanent traps that rely on tidal differences to hinder the passage of fish, often catching many types of marine species.

Writing in the ICES Journal of Marine Science, lead researcher Dalal Al-Abdulrazzak, a PhD student with the UBC Sea Around Us Project, and his colleages, report that the help of modern technology is enabling them to finally get a better picture of the region's large-scale fishing operations.

"This ancient fishing technique has been around for thousands of years," Al-Abdulrazzak said. "But we haven't been able to truly grasp their impact on our marine resources until now, with the help of modern technology."

In the research abstract, the authors say the study speaks to "the unreliability of officially reported fisheries statistics" and provides the first example of fish take estimates from space.

"Time and again we've seen that global fisheries catch data don't add up," Daniel Pauly, principal investigator with the Sea Around Us Project and the study's co-author, said in a statement.

"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," Pauly said.

The researchers say their work shows the potential for using remote sensing approaches to validate fish take statistics and fisheries operations in general.

More Google Earth images of the weirs can be seen here.