The area, an icy sea far outside the reaches of most countries and their navies, is an inhospitable region frequented only by research vessels and intrepid fishing boats. It is also home to the Patagonian toothfish, which some say is the best-tasting fish in the world.

Living much of its adult life in ice-cold waters more than 1,000 metres down, and barely known until the 1980s, its meat is considered a delicacy, having a taste somewhere between lobster and scallop. One British restaurant critic wrote that it is “seriously endangered, so you’d better eat as much as you can while stocks last”.

Described in the book as a “petulant and repulsive giant that can grow to a weight of 120 kilograms and live more than 50 years”, the Patagonian toothfish (also known as the Chilean sea bass) is a “deep sea delicacy that can be just as profitable as narcotics or human trafficking”. In the wild west waters around the Antarctic, this makes it a tempting proposition.

In 2014, the Thunder, a notorious poaching vessel, was part of a group of ships known as the “Bandit 6”, which illegally fished Antarctic waters for years, earning their secretive owners tens of millions of dollars in the process. The Bob Barker, meanwhile, with its crew of 31, is part of Sea Shepherd, a more militant environmental group that grew out of Greenpeace – its flag bears the skull of a pirate flag, but with the crossbones replaced by a shepherd’s crook and a trident.

Sea Shepherd had previously been a thorn in the side of Japanese whalers. However, with whaling in decline, the group decided to home in on a new target: the Bandit 6.

These vessels included the Thunder, the Viking, the Kunlun, the Yongding, the Songhua and the Perlon – although each went by many names. They had been plundering the stock of Patagonian toothfish for years, gliding in and out of ports, mostly in Asia, to dis­charge their illegal cargos. While their officers were predominantly Spanish and South American, the deck crews were hired from Asian countries such as Indonesia.

Many of the vessels were wanted by Interpol, and all had been blacklisted by the Convention on the Conservation of Antarctic Marine Living Resources, the organisation that manages the maritime resources surrounding Antarctica. However, this didn’t stop their activities: the Norwegian-built Thunder is estimated to have earned its owners more than US$60 million from poaching.

This was what the Bob Barker and its 30-year-old Swedish-American captain, Peter Hammarstedt, were up against when they decided to take on the Thunder.

Sailing into frigid waters in search of their target, they watch the radar for telltale signs of slow-moving dots out of sync with the shifting icebergs. Within two days they have located the Thunder and, after an initial game of chicken through the pack ice, the boats settle in for a long chase, each wary of the other but unwilling to resort to extreme measures.

The Bob Barker hopes to trail the Thunder to port, keeping Interpol and national authorities up to date with their movements so navies and coastguards can be prepared. The Thunder and its crew, meanwhile, simply want to lose their tail and vanish. The ships’ captains communicate tensely with one another over the radio, each trying to persuade the other to give up.

Catching Thunder is about more than just the pursuit of one ship, however. Its main focus is the years-long efforts to track these vessels and their mysterious owners on both sea and land. Beyond attempts to bring the ships’ owners to justice, the book explores the challenges involved in trying to police international waters far from populated areas.

In 2012, Norway and the United States took the initiative, creating a committee to combat illegal, unreported and unregulated fishing, and later that same year, Interpol carried out its first covert operation against fish poachers. The task though is daunting, and made all the more difficult by the ease with which ships register in places such as Togo, Nigeria and landlocked Mongolia, the latter having a navy that consists of one tugboat, with a crew of seven, only one of whom can swim, according to the authors.

These countries sell ship registration with few questions asked, offering legitimacy to owners who want to operate outside the law but scant ways to trace them. When an official at the Nigerian coastguard starts digging into the Thunder partway through the chase, he finds a confusing situation. The vessel has been registered in Nigeria four years earlier by a shipping agent using the address of a bankrupt amusement park in Lagos. The amusement park, once popular, is now inhabited by petty criminals and vagrants, with one corner used as a makeshift cemetery.

Seeking even more layers of protection, many of the vessels have multiple identities, backed up with legitimate paperwork, so that when threatened they can switch name plates and in minutes change their designation to evade pursuit: the Kunlun had at least 10 names over a decade and had been flagged in five countries.

Following the money trail proves harder still, with the profits hidden in tax shelters and only a handful on board aware of the identities of their real bosses. Despite the lengths to which the owners go to hide their involvement, the trail eventually leads to Europe, to a region with a history of smuggling and involvement in the cocaine trade.

The authors take readers on a journey as they seek to come face-to-face with those profiting from poaching, and realise the challenges involved in bringing them to justice. One of the book’s strengths is that Engdal and Sæter track down players on both sides, telling the story from all angles. We get the experiences of the environmental­ists, the officers on the fishing vessels, the Indonesian crews, and even of those involved in the operations on land.

Eventually, the gruelling sea chase starts to weigh heavy on all those on board. At one point, fearing the Indonesians on the Thunder are being mistreated, the crew of the Bob Barker put translated messages into bottles and throw them aboard the other ship.

When the Thunder begins to run out of fuel off the coast of the tiny island state of São Tomé and Principe, off the western coast of Africa, tension builds again with the fear of violence and the need to gather evidence before it vanishes.

This is a story to keep in mind next time you’re given the option of ordering Patagonian toothfish or Chilean sea bass in a restaurant.