Finally, it's hard to determine who the real perpetrators are — even when violating boats are identified. Illegal fishing vessels change names and intentionally obscure their ownership.
A vessel at sea may be owned by a person in one country, fly the flag of another country, be captained by someone from a different country, and put its cargo ashore in yet another — for processing somewhere else, and sale somewhere beyond that.
And there's nothing illegal or inherently unethical about a globalized fishing industry, or practices such as transshipping that support it.
But the practices that underpin global shipping can become problems in their own right, such as when criminal boats dump their cargoes onto mother ships, where illegally caught fish may get mixed in with catches from other boats — including the legal ones.
Those illegal catches, blended in with the rest, then become untraceable.
WATCH: "Oceans of Crime" premieres in the U.S. on Saturday, February 17 at 8 p.m. ET/PT. It premieres in Asia starting on Monday, February 19 at 1 p.m. SIN, and in Europe on Monday, February 19 at 1 p.m. CET.