Computers have crunched 22 billion identification messages transmitted by sea-going vessels to map fishing activity around the globe.
The analysis reveals that more than 55% of the world’s oceans are subject to industrial exploitation.
By area, fishing’s footprint is now over four times that of agriculture.
That’s an astonishing observation given that fisheries provide only 1.2% of global caloric production for human food consumption.
The investigation shows clearly that the biggest influences on this activity are not environmental – whether it is summer or winter, or whether there is an El Niño or fish are migrating, for example.
Rather, the major controlling factors are very largely political and cultural.
“You’d think that fishing activity would follow some natural pulse of the seasons, but in fact that’s secondary to whether it’s a weekend or not, or whether there’s a moratorium, or a public holiday,” says David Kroodsma from Global Fishing Watch, which led the study published in Science Magazine.
“Because fishing is an industrial activity tied to politics and culture, this is actually a positive message because it shows we have a lot of human agency in the way we fish the oceans, and it’s entirely within our power to change things,” he told BBC News.
Kroodsma and colleagues have been playing with the data coming from the transponders that all large vessels are now mandated to carry.
This Automatic Identification System (AIS) means each boat will push out information every few seconds about its position, course, and speed.
These messages can be detected from space by satellites, and recent years have seen increasing numbers of spacecraft launched just to track what’s happening on the high seas.
Kroodsma’s team looked at the data from 2012 to 2016. It encompasses the messages from over 70,000 vessels. That’s far too many boats and too much data for individuals to comb through.
So, the team has trained algorithms to do the work instead – to recognise in the movement of the vessels behaviours such as whether they actually have gear in the water and what sort of gear that might be. Nets or longlines, for example.
The team is able to produce “heat maps” to illustrate where fishing activity is most intense – such as in the northeast Atlantic and northwest Pacific, as well as in nutrient-rich regions off South America and West Africa.
Remarkably, it is the fleets from just five countries (China, Spain, Taiwan, Japan, and South Korea) that account for more than 85% of observed fishing effort on the high seas, i.e. away from their exclusive economic zones.
The team says that over the course of the study period, the analysis recorded over 37 million hours of fishing.
Read the full article at BBC News and access the data at Global Fishing Watch.