While that mission is routine to the Coast Guard, it was the first time an aircraft carrier was involved in fighting illegal fishing in Oceania, a vast region northeast of Australia. Officials say Oceania is important not only to U.S. economic prosperity, but also 22 Pacific island nations financially dependent on their local fisheries. A key area is what’s known as the “Tuna Belt,” which runs along the equator and supplies 57 percent of the world’s tuna. Many livelihoods are threatened by illegal fishing, said Coast Guard Cmdr.