As the Thunder, a trawler considered the world’s most notorious fish poacher, began sliding under the sea a couple of hundred miles south of Nigeria, three men scrambled aboard to gather evidence of its crimes. In bumpy footage from their helmet cameras, they can be seen grabbing everything they can over the next 37 minutes - the captain’s logbooks, a laptop computer, charts and a slippery 200-pound fish.The video shows the fishing hold about a quarter full with catch and the Thunder’s engine room almost submerged in murky water. “There is no way to stop it sinking,” the men radioed back to the Bob Barker, which was waiting nearby. Soon after they climbed off, the Thunder vanished below.It was an unexpected end to an extraordinary chase. For 110 days and more than 10,000 nautical miles across two seas and three oceans, the Bob Barker and a companion ship, both operated by the environmental organisation Sea Shepherd, had trailed the trawler, with the three captains close enough to watch one another’s cigarette breaks and on-deck workout routines.In an epic game of cat-and-mouse, the ships maneuvered through an obstacle course of giant ice floes, endured a cyclone-like storm and nearly collided in what became the longest pursuit of an illegal fishing vessel in history.Industrial-scale violators of fishing bans and protected areas are a main reason more than half of the world’s major fishing grounds have been depleted and by some estimates over 90 percent of the ocean’s large fish like marlin, tuna and swordfish have vanished. Interpol had issued a Purple Notice on the Thunder (the equivalent of adding it to a Most Wanted List, a status reserved for only four other ships in the world), but no government had been willing to dedicate the personnel and millions of dollars needed to go after it.So Sea Shepherd did instead, stalking the fugitive 202-foot steel-sided ship from a desolate patch of ocean at the bottom of the Earth, deep in Antarctic waters, to any ports it neared, where its crews could alert the authorities. “The poachers thrive by staying in the shadows,” said Peter Hammarstedt, captain of the Barker, said while trying to level his ship through battering waves. “Our plan was to put a spotlight on them that they couldn’t escape.”The pursuit of the Thunder until its sinking in April, pieced together from radio transmissions, interviews, ship records and reporting on board the Bob Barker and its fellow ship, the Sam Simon, demonstrates the anything-goes nature of the high seas, where weak laws and a lack of policing allow both for persistent criminality and, at times, bold vigilantism.Banned since 2006 from fishing in the Antarctic, the Thunder had been spotted there repeatedly in recent years, prompting Interpol to issue an all-points bulletin on it in December 2013.'Maintain Hot Pursuit’On its second day of prowling for the Thunder last December, the Barker spotted its prey.Hammarstedt radioed the Thunder’s officers, most of them Spaniards or Chileans. Speaking through a translator, he warned that the Thunder was banned from fishing in those waters and would be stopped.The Thunder responded: “No, no, no. Negative, negative. You have no authority to arrest this vessel. You have no authority to arrest this vessel. We are going to continue sailing, we are going to continue sailing, but you have no authority to arrest this ship, over.”“We do have authority,” the Bob Barker said. “We have reported your location to Interpol and to the Australian police.”The poachers replied, “OK, OK, you can send our location, but you can’t board this ship, you can’t come in or arrest us.”The Thunder’s crew, which had been working on its aft deck, abruptly disappeared inside. The ship (a trawler that had been converted to do other types of deep-sea fishing) soon doubled its speed and made a run for it, the Barker close behind. They were in a stretch of Antarctic sea called the Banzare Bank, known among mariners as “The Shadowlands” because it is among the planet’s most remote and inhospitable waters, nearly a two-week journey to the nearest major port.On that first night of the chase, Dec. 17, Hammarstedt made a note in his ship’s log: “Bob Barker will maintain hot pursuit and report on the F/V Thunder’s position to Interpol.”On Feb. 7, tensions erupted. After the Thunder threw out fishing nets, Hammarstedt tried blocking the ship’s path. The Thunder responded by charging toward the Barker. Hammarstedt immediately pulled his throttle into reverse, avoiding a collision by about one yard.The next day, the Thunder’s deckhands began preparing their nets, with officers radioing beforehand to alert the Barker that they intended to fish. “If you do, we will cut your nets,” Hammarstedt threatened.Moments later, as the Thunder’s mesh hit the water, he gave his crew the go-ahead. They began lifting and cutting the buoys, causing the nets to sink. The Thunder’s captain, Alfonso R. Cataldo, 48, exploded.“You are taking our buoys!” he said over the radio. “That is illegal. We are coming.”The Barker responded that it had seized the fishing gear as evidence of a crime.“We are coming next to you to get our buoys,” the Thunder’s captain replied angrily. “You have to give them back.” Shortly after, he added: “You started this war.”Turning the chaser into the chased, the Thunder headed full throttle at the Bob Barker, which fled. Three hours later, the Thunder’s captain returned to his original course.Offering Help, With Caution The distress call came at 6:39 a.m.“Assistance required, assistance required,” the Thunder’s captain pleaded over the radio. “We’re sinking.” The Thunder had collided with something, he said, possibly a cargo ship. “We need help.”The Sea Shepherd officers were shocked. While they noticed some commotion on the Thunder, there was no hint of a collision. Still, they quickly agreed that the more spacious Sam Simon would take the Thunder’s crew on board.At 12:46 p.m. on April 6, the Sam Simon’s log noted of the Thunder: “Going down very fast.” By then, the trawler’s crew had moved into their rescue boats. Meanwhile, three Barker crewmen were climbing on board in hopes of salvaging evidence.“I’m giving you 10 minutes,” Hammarstedt said in a radio call to his men.After grabbing binders, charts and computers from the bridge, they headed to the engine room, finding it almost completely submerged.Helmet camera footage shows hundreds of white plastic bags - stacks of wrapped fish (just “trunks,” their heads, tails and guts removed).The nearest port officials in São Tomé and Príncipe, the small island nation off the coast of West Africa, were contacted.On arrival, the Thunder’s senior crew members were arrested. In July, three officers were charged with a variety of counts, including pollution, negligence and forgery. Several other governments are considering charges against the ship’s owners for illegal fishing and perhaps other crimes, including money laundering and tax evasion, according to the Interpol official who discussed the case on the condition of anonymity.But losing the ship - and the evidence that went down with it, including the fish in the hold, onboard computers, various records and fishing equipment - makes prosecution more difficult, Interpol and Sea Shepherd officials acknowledge.The Sea Shepherd’s crew, along with law enforcement authorities, are suspicious about how the great chase ended. No other vessels had been near the Thunder before it sank, and its cabin doors were tied open rather than sealed shut to keep water out. That suggested the $5 million ship might have been intentionally scuttled, possibly to avoid being seized by the police, according to the authorities in São Tomé and Príncipe and Sea Shepherd officials.The Sam Simon crew remembered something else. As their ship carried the Thunder’s crew back to land, Cataldo climbed onto a 5-foot-high stack of his confiscated nets on the back deck. Stretching out, he went to sleep.But just before that, as the Thunder finally sank, he had pumped his fist and cheered.--2015 New York Times News Service..