Our industrial fishing fleets traverse an area of ocean four times larger than all the agricultural land on earth. That’s just one of many findings in a new study which tracks 70,000 fishing vessels between 2012 and 2016 and shows in unprecedented detail where they go, and what drives their activities. The results, published in Science, were also used to generate an interactive, public map which reveals the industry’s surprising extent.
The study takes advantage of new technological developments in the automatic identification signals (AIS) that vessels transmit–and which are now being used in international efforts like Global Fishing Watch to track the scale of fishing at sea. The huge breadth of the data the researchers gathered enabled them to reveal some surprising unknowns. In 2016 alone fishing vessels logged 40 million hours of fishing activity, which equated to 19 billion kilowatt hours of energy consumed, they found. Fishing occurs over at least 55% of the planet–concentrated in regions like the northwest Pacific and northeast Atlantic. This covered more than 200 million square kilometres of ocean–many times the area that agriculture covers on land. And yet despite this, fishing contributes only 1.2% of our global calories.
Intriguingly, the high-resolution data highlighted something that hadn’t been much considered before: the impact of culture and politics versus environmental factors on fishing patterns. In the mid-latitudes, there was a notable dip in activity which seemed to coincide with the moratorium on fishing in China. In the Northern hemisphere–around Europe–activity plunged in the days around Christmas. Similarly, there were fewer Chinese vessels detectable over the Chinese New Year.
This might not seem all that surprising. But what is unexpected is that compared to these cultural and political features, natural factors like changes in fish populations and migration made far less of an impact on how fishing patterns took shape. Like other major industries on earth, the authors conclude, fishing today appears to be relatively insulated from natural cycles–determined to a surprising degree by human factors instead.
The analysis also highlighted some regions of lower fishing activity, such as in the Southern Ocean. It showed that a handful of nations–China, Spain, Taiwan, South Korea, and Japan–dominate on the high seas, accounting for 85% of fishing there. (Most other countries’ vessels appeared to confine their activities to the exclusive economic zones of their respective nations.)
To get their results the researchers used cutting-edge machine learning tools to accurately recognise fishing vessels by their AIS, and identify features such as their length, tonnage, and engine power to yield detailed information about their activities. Ultimately, the platform processed 22 billion individual AIS signals to build up the vast, global picture.
Its insights into the nuances of industrial fishing could help us better manage the ocean’s biodiversity. For instance, live mapping can reveal unfished zones where conservation could have a bigger impact. It could help keep track of the biggest fishing nations and how much they fish, and may even assist governments in identifying which fishing policies are working, and which are not. By bringing fishing activities into a transparent, online realm, the study’s open, accessible map has also given everyone a stake in understanding the scale of the threat it poses to our seas.
Source: Kroodsma et. al. “Tracking the global footprint of fisheries.” Science. 2018.