One moment the undersea is featureless blue, an empty cathedral, the sun an undulating hot spot in the vault of waves overhead, its beams radiating down as if from stained glass. The next moment the ocean is full of giant, bomb-shaped bluefin tuna, the largest measuring 14 feet long and weighing three-quarters of a ton. In the sea’s refracted sunlight, their pale flanks flare and scintillate like polished shields. Their fixed fins—the long, curved anal fin and the second dorsal—flash like sabers. Their quick-sculling tail fins drive the formation forward at ten knots, with sprints to 25, a ceaseless, staccato beat. And just as suddenly they are gone. The ocean is empty again. Here and there a small galaxy of scales marks where a bluefin swallowed a herring. The victim’s scales swirl in the turbulence of the departed tuna, now bearing off at high speed. Then each vortex slows and stops. The sinking scales gleam like diamonds from a spilled necklace. Then they dim. Finally they wink out with depth. The true tunas, genus Thunnus, are supercharged fish, streamlined to perfection and jammed with state-of-the-art biological gear. The characteristics that distinguish the true tunas include great size, great range, efficient swimming stroke, warm bodies, large gills, finesse at thermoregulation, rapid oxygen uptake, high hemoglobin concentration, and clever physiology of the heart. All of these reach their apogee in the bluefin.
The three species of bluefin—the Atlantic, Pacific, and southern—have divided the world’s oceans among themselves, and they roam all planetary seas except the polar. The bluefin is a modern fish, yet its relationship with humanity is ancient. Japanese fishermen have caught Pacific bluefin for more than 5,000 years. The Haida of the Pacific Northwest have hunted the same species for at least as long, based on the evidence of bluefin bones in their middens. Stone Age artists painted Atlantic bluefin tuna on the walls of Sicilian caves. Iron Age fishermen—Phoenician, Carthaginian, Greek, Roman, Moroccan, Turkish—watched from promontories for the arrival of bluefin schools at their Mediterranean spawning grounds.
“Bluefin helped build Western civilization,” Stanford University professor Barbara Block, a preeminent scholar of this fish, told me. “Across all the Mediterranean, everybody netted giant tuna. The bluefin have annual migrations in through the Strait of Gibraltar, and everyone knew when they came. In the Bosporus there were 30 different words for bluefin. Everyone put out net pens that had different names in the different countries. Penning created cash. Bluefin were traded. The coins of Greece and Celtic coins, they had giant bluefin on them.”