Official fisheries catch statistics in developing countries can be sometimes unreliable, especially when faced with limited resources for collecting statistical data. Misreporting catch data has strong implications for food security, resource conservation, and understanding regional and global trends in marine ecosystems.
Al-Abdulrazzak and Pauly describe a methodology that allows for the verification of reported fish catches using freely-available Google Earth imagery. By scanning the coast of the seven countries around the Persian Gulf, the authors were able to count large tidal fish traps or weirs, whose catches are often omitted from officially reported data. By combining the estimated number of traps – which also account for likely present, but unseen traps - with assumptions about their daily catch and the duration of their fishing season, the authors were able to estimate annual catches that are up to six times more than what is officially reported for the Persian Gulf as a whole.
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. Thus, in addition to the disparity between reported and estimated catches, the authors were also able to expose illegal fishing as some weirs they observed were operating in countries where the traps are banned.
Because of the near global coverage of satellite imagery, and because images are repeatedly captured over the same area, their methodology, which can be straightforwardly adapted to other fixed gears, provides a cost-effective way to monitor large areas of the ocean.
Google Earth view of a fishing weir off the Kuwait coast