When excavators dug what would become subway tunnels beneath Boston in 1915, they found thousands of wooden stakes, remnants of an ancient, stationary fishing trap known as a weir. This one was huge, installed to corral hundreds of thousands of fish as they attempted to swim to deeper waters during the ebb tide. And it was not just old – it was a fixture of life. Carbon dating revealed the trap, now known as the Boylston Street Fishweir, was first installed 5,700 years ago, and that it was used and maintained over a period of 1,500 years.
As technology goes, fish weirs are among humanity’s oldest, and, judging by their continued worldwide use, most irreplaceable. So it is a little ironic that one of the newest technologies – satellite imagery – was used to expose the present-day use of weirs to overharvest commercial fish species. In a recent study published online in the ICES Journal of Marine Science in November 2013, researchers employed Google Earth to count the number of fishing weirs sited off of six Persian Gulf nations: Kuwait, Bahrain, UAE, Iran, Saudi Arabia, and Qatar.1 Using Google Earth images, local and regional data on catch volumes, and data about types of fish caught, the researchers created a model for the likely yearly catches at the studied weirs. What they found may have been fit for a detective novel – mismatches between officially reported catch data and estimates including fish catches using weirs.
Across all six countries, the study estimated that 31,433 tons of fish were caught in weirs in 2005. This number was six times higher than the 5,260 tons reported to the Food and Agriculture Organization. The researchers estimated that in Bahrain alone, catch volume from weirs was 142 percent greater than the total volume that country reported for all types of fishing. Perhaps even more striking, Iran reported that no fish were caught in weirs in 2005, while the study estimated 12,000 tons of fish were caught in Iranian weirs that year.
While the study’s methods are novel and limited in geographic scope, they have the potential to be applied on a much broader basis to provide greater insight as to the true sustainability of fishing practices, and to shed new light on the health of global fisheries. The authors stress that the six countries studied are not alone in their negligence. The study, they assert, is just representative of a larger global misreporting problem. Satellite data is a new tool – similar to the way the fishing industry has used technology like Fishfinders and GPS Chartplotters to target catches – to monitor fisheries, particularly in areas that were previously considered too remote or expensive to patrol, according to the authors. With satellite technology comes expanded capacity to monitor fisheries, forests, and land-use in ways that complement the old tools.
1 Al-Abdulrazzak, D. and Pauly, D. (2013) Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science, published online, 25 November 2013, doi: 10.1093/icesjms/fst178.