Government authorities and shipping industry insiders are increasingly concerned that maritime piracy will rise globally as huge, commercial fishing firms—especially the ones that operate illegally—drive fishermen from poor countries out of business.

Local fishermen who have plied their trade for generations in Latin America, Africa, Asia and even Northern Europe increasingly find their livelihood threatened by commercial fishing operations whose scale and more advanced vessels are just too much to compete against.

Though it's impossible to quantify how many pirates were once fishermen, experts agree that many small fishermen have turned to stealing from big merchant ships as their fisheries have been wiped out.

"When people don't have any way of feeding their families by fishing, they don't have many options," meaning some will turn to maritime crime, said Lisa Speer, director of the international oceans program at the Natural Resources Defense Council.

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Countries that border on an ocean all have a 200-mile boundary within which they have exclusive fishing rights. (Exclusive economic zones extend much further into the ocean than "territorial waters" do.) But poorer countries often don't have the naval craft needed to patrol and protect their own rightful economic zones.

The problem is exacerbated by commercial fishing companies that fly "flags of convenience" on their ships. Companies illegally poaching on a country's fishing rights often fly the national flag of some third-party nation—usually one that can't or won't exert control over its own flagged vessels—in order to conceal their true identities and avoid international laws, according to a 2012 report from the Food and Agriculture Organization of the United Nations.