Catch statistics are fishy

By Dalal Al-Abdulrazzak

Despite their wide usage, global fisheries catch data compiled by the United Nations Food and Agriculture Organization (FAO) are questionable.

In our study, we use Google Earth satellite images to examine fish weirs, a type of trap that works with the changing tides. Using the Persian Gulf as a case study, we combine the estimated number of traps—which accounts for likely present, but unseen traps—with assumptions about their daily catch and fishing season length to estimate annual catches for the region that are up to six times more than what is officially reported but Gulf countries.

These results, which provide the first example of fisheries catch estimates from space, speak to the potential of satellite technologies for monitoring fisheries remotely, particularly in areas that were once considered too dangerous or expensive for fisheries surveillance and enforcement. For example, we were able to reveal and account for 17 illegal operating traps in Qatar, and suggest that similar methods can be used to expose other illegal marine practices such as monitoring activities in Marine Protected Areas (MPAs) and assessing the magnitude of oil spills.

Because of the near global coverage of satellite imagery, and because images are repeatedly captured over the same area, our methodology can easily be adapted to other fixed gears and provides a cost-effective way to monitor large areas of the ocean. By coupling satellite images with robust data we are able to more accurately assess human impacts in marine ecosystems (however it is still up to people to better manage these impacts).

Numerous other studies have also shown that fish catches are not what the national agencies report, often due to limited resources, historical legacies, or political interference. For example, when biological models could not explain the global increases in fish catches, scientists realized that Chinese officials were intentionally inflating their catch statistics. When these figures were accounted for, models showed that global catches were in fact decreasing, not increasing.

Misreporting catch data has non-trivial consequences that extend far beyond fisheries sustainability and can lead to policy decisions that jeopardize food security, underestimate the contribution of small-scale fisheries to rural food security and GDP, and potentially lead to overoptimistic management plans or between-country access agreements.

Dalal Al-Abdulrazzak is PhD Candidate at the University of British Columbia’s Fisheries Centre where she is researching long-term changes in the marine ecosystems and fisheries of the Persian Gulf. Along with Daniel Pauly, she is co-author of the paper ‘Managing fisheries from space: Google Earth improves of distant fish catches’ in the ICES Journal of Marine Science.

The ICES Journal of Marine Science publishes articles, short communications, and critical reviews that contribute to our scientific understanding of marine systems and the impact of human activities. The Journal serves as a foundation for scientific advice across the broad spectrum of management and conservation issues related to the marine environment.

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Image credit: Satellite image of the Persian Gulf. By NASA [Public domain], via Wikimedia Commons