The following is an excerpt from Kings of Their Own Ocean: Tuna, Obsession, and the Future of Our Seas, by Karen Pinchin.

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Kings of Their Own Ocean: Tuna, Obsession, and the Future of Our Seas by Karen Pinchin

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In the middle of the Atlantic Ocean, between swells of blue‑gray water, the sky is a dome over a dinner plate, vast and variable. The horizon’s flatness cleaves a line through the elements, a trick of perspective obscuring the earth’s true curvature. On an unpredictable sea, the permanence of that line, its physical declaration of up and down, anchors a reality a seafarer can cling to, a reality without which she—or you, or I—could lose herself.

At exactly 45° west longitude, between the coasts of North America and Europe and hundreds of kilometers from the nearest land, there’s another line. This one cuts the ocean perpendicular to the horizon and runs vertically from surface to seafloor. Plummeting downward along this vertical cross section, dropping through watery layers, white sprays are tossed from wave tops; clouds of plankton and krill drift languidly; the sunlight fades and eventually disappears. Spidery starfish creep along the sandy seafloor past lurking wolffish. From spitting surface to deepest undersea canyon, these strata take shape in my imagination like a painting in one of my son’s picture books.

Ever since this line at the 45° west meridian was invented by humans, it has dictated the fortunes and fate of Atlantic bluefin tuna, one of our planet’s most spectacular and vital apex predators. The line is also entirely theoretical, except to the extent that it controls a billion‑dollar industry and has allowed humans to run roughshod over one of the world’s most contested species for decades.

Atlantic bluefin tuna, Thunnus thynnus, have lived for millions of years in our physical world and captured human imaginations long before the written word. Ancient peoples trapped bluefin in shallows and killed them with rocks and sticks; Greeks and Phoenicians immortalized the economically important fish in art and theater, and even stamped its image on early currency. Bluefin are “charismatic megafauna”—a category of large, big‑eyed beasts including elephants, lions, and whales that serve as placeholders in the public imagination—and have come to represent the health of our oceans and the overfishing that besieges them.

Compared with floppy, schooling fish, giant bluefin are more machine than fuel, more predator than prey. I was in my mid‑20s when I first saw one in person, and it fit my idea of “fish” as much as a dinosaur resembles a chickadee; there was, from that initial impression, a problem of scale. The largest tuna ever caught weighed 1,496 pounds, if you can imagine a grand piano shaped like a nuclear weapon. To stand beside a just‑landed giant bluefin, still slick from salt water, feels akin to standing beside a natural marvel like Niagara Falls or an erupting volcano. There’s beauty, but also danger. 

Every late summer and early fall, schools of gorgeous, massive bluefin rocket along North America’s Atlantic coast. They are an advanced rod‑and‑reel sport fisherman’s fish: catching one requires time and a full set of pricey and intensely specific gear, including a volleyball‑sized brass reel built to handle a tuna’s heft. Some fishermen call bluefin “marauders”; others, “racers.” The genus name Thunnus, after all, comes from the ancient Greek word θύνω, or thuno: rush.

Throughout the mid and late 1970s, the world’s three bluefin tuna populations—Atlantic, Pacific, and Southern—plunged globally because of rampant overfishing, largely due to demand for the sushi‑grade fish in Japan. In 1981, two dozen tuna‑fishing countries made their first move to restrict the trade, drawing a line down the middle of the Atlantic Ocean during a meeting hosted by the Spanish government in Madrid. That line ran from the southernmost tip of Greenland, zigzagged around Brazil’s rocky bulge, then progressed south off the map toward Antarctica. Starting the following year, all bluefin tuna caught to the right of the line toward Europe and North Africa would be considered “eastern” fish, while all to the left would be “western.” At the time, prevailing scientific thought held that the powerful, warm‑blooded fish largely gravitated back to the coastlines where they were born, with eastern fish spawning in the balmy Mediterranean and their western counterparts in the Gulf of Mexico.

Overnight, this conceptual line transformed the fisheries for Atlantic bluefin tuna. Toward the European side of the Atlantic Ocean, harvests remained a free‑for‑all with no quotas on how many fish could be caught and killed for the countries that had historically fished those waters.

Toward North America, for countries including the United States and Canada—and for historical reasons, Japan—not a single fish, other than those purportedly caught for “scientific purposes,” could be legally caught. Called the two‑stock theory, this understanding of how tuna breed and migrate, as two almost entirely separate populations, set the stage for how Atlantic bluefin have been protected and managed for the entirety of my lifetime.

Since the 1970s, global bluefin tuna populations have surfed the curling edge of collapse. Bluefin tuna flesh is tasty and nutritious, qualities that helped fuel the rise of the Phoenician and Roman empires. Despite making up only 1 percent of the world’s tuna catch—other species include albacore, yellowfin, and bigeye—bluefin tuna makes up nearly two‑thirds of its value. Since Mediterranean fishermen employed huge nets to catch bluefin en masse 3,000 years ago, demand for the fish has existed in uneasy balance with its natural ability to reproduce and thrive. And despite billions of dollars spent, decades of scientific research, and numerous campaigns to “Save the Bluefin,” that remains as true today as it was decades ago.

Amelia inspired my own journey into the purpose and meaning of science and its limitations, including an exploration of how far we’ve come—and how far we’ve yet to go. And as I lost myself in the ocean, traveling alongside Anderson and Lutcavage’s fish, I passed signals and signs of greater upheavals: conflict over global fishing rights, bluefin poaching, and the future of our food supply in a changing climate. For years, Amelia crossed the Atlantic Ocean and evaded capture. She ate and spawned and grew. Humans caught her, and then caught her again. Finally they killed her.

Over those same decades, the people who touched her flanks experienced their own triumphs and tragedies, losses and redemptions. If everything my parents taught me about science is true—if facts are indeed the sun around which we all orbit—then puny human emotions can’t hold a candle to the ocean’s scale and its untouchable power. Yet around every bend of this journey, I found both human and animal existences amplified: the exquisite ache of failure; the tightrope walk of existence; serene joy in our planet’s offerings and deliverance; and ultimately how quickly it all can end. What started as a simple fish story showed me a world where bold scientific, commercial, and personal endeavors can crystallize into a single burning vision. But occasionally those visions collide, sometimes leaving their bearers forlorn, other times carrying them to the greatest heights. And often science itself, the tool and technique through which we grasp for certainty in an uncertain world, has little to do with who, or what, wins or loses.

Diving into the history of bluefin and the human communities that have lived alongside the species for millennia, I glimpsed a vision of a reciprocal future, one in which human passions could dovetail with our long‑term survival on this planet—a quest that must include the right of wildlife to thrive alongside us. I discovered we all need our own versions of that 45° line: a boundary to anchor us, others to hold us, or even a small sense that this all might mean something in the end.

But before reaching for dry land, we must first enter the sea.

From Kings of Their Own Ocean: Tuna, Obsession, and the Future of Our Seas by Karen Pinchin, with permission from Dutton, an imprint of the Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2023 by Karen Pinchin