https://phys.org/news/2018-08-fishing-fleets-fish.html

"While most countries continue to focus their fishing efforts on local waters, Taiwan, South Korea, Spain and China have aggressively subsidized vessel and fuel costs to encourage their fleets to operate thousands of kilometres from their home ports," said lead author David Tickler, a postgraduate student at UWA's School of Biological Sciences.

Despite this geographical expansion, the catch rates of these fleets—as well as those of the other top 20 fishing countries—have declined dramatically from over 25 tonnes per 1000 kilometres travelled in the early 1950s to approximately 7 tonnes per 1000 kilometres travelled by 2014. Overall, these 20 countries are responsible for 60 million tonnes or 80 per cent of the global industrial fishing catch.