But China, with its enormous population, growing wealth to buy seafood and the world’s largest fleet of deep-sea fishing vessels, is having an outsize impact on the globe’s oceans.

Having depleted the seas close to home, Chinese fishermen are sailing farther to exploit the waters of other countries, their journeys often subsidized by a government more concerned with domestic unemployment and food security than the health of the world’s oceans and the countries that depend on them.

Increasingly, China’s growing armada of distant-water fishing vessels is heading to the waters of West Africa, drawn by corruption and weak enforcement by local governments. West Africa, experts say, now provides the vast majority of the fish caught by China’s distant-water fleet. And by some estimates, as many as two-thirds of those boats engage in fishing that contravenes international or national laws.

China’s distant-water fishing fleet has grown to nearly 2,600 vessels (the United States has fewer than one-tenth as many), with 400 boats coming into service between 2014 and 2016 alone. Most of the Chinese ships are so large that they scoop up as many fish in one week as Senegalese boats catch in a year, costing West African economies $2 billion a year, according to a new study published by the journal Frontiers in Marine Science.