Fast Fish: The Ocean's Hidden Talent

We will always be strangers to water. For all the liters running through our veins, marine environments chill us, smother us, bind us up in dragging coils and even warp our perception. You can likely picture a car going 30 miles per hour, but what about a ship going 15 knots? If you were to guess at the speed of the world's fastest fish, what reference frame would you even use to estimate? As a species, we're not good at understanding water.

Neither are we talented at traversing it. The fastest Olympian swimmers manage barely six miles per hour; a goldfish in your local pet store beats that easily! Whether speed is deployed for hunting, evasion or entertainment, the sea's daily dramas play out much more quickly than we realize.

The fastest fish in the world is the sailfish, part of a larger "billfish" family including swordfish and marlin. They're fast, powerful predators clad in sheets of taut fast-twitch muscle under chrome scales. Like tuna and mahi (muscular predators make for good eating), sailfish zip through open-ocean waters at high speed looking for schools of small schooling fish. With tactical flashes of their proud sail-like fins, they gather their prey into roiling silver globes before lunging in with rigid bills. A single swipe stuns a small creature, knocking it senseless, rendering it helpless.

Here the real challenge begins. The sailfish is likely traveling at nearly 60 miles per hour to hunt, though bursts of 60 miles per hour have been recorded. Eating at such high speed is tricky to say the least. The fish's bill might be just two feet long, allowing a window of less than a tenth of a second in which to gulp the meal. Imagine driving to work in the morning, only instead of stopping at a stand for coffee you've got to reach out and snatch your steaming paper cup off the asphalt without braking. This is difficult even for sophisticated predators, and even more so when those predators are cold-blooded animals swimming in cold water! To keep their brains and eyes from growing sluggish in the chill, sailfish have evolved heating organs inside their skulls. Efficiently turning calories into warmth, they maintain top physical and mental performance at all times.

Predators aren't the only species making use of speed -- overmatched prey have always relied on flight over fighting. Enter the dubiously named flying fish. The aerial sprints for which they're known take place at impressive speed, up to 30 miles an hour above the water's surface. These flights are responses to predators below. When threatened, an entire school of flying fish will hit the proverbial jets and take to the skies. It's effective in the moment, but against persistent predators they quickly face a harsh reality: they're not truly flying. They can't beat their wing-like fins fast enough to generate lift and so after that initial jump they're merely gliding. What goes up must come down, and mahi often chase just below the surface. They can match the flying fish's aerial speed underwater, so they push their muscles hard and stay patient.

The flying fish has only one way to keep herself aloft. As she falls back to the sea's embrace, the elongated lower lobe of her tail fin is the first body part to strike. She hurls all her strength into her tail, whipping it back and forth 60 times each second, effectively whirling it into a propeller. The lobe slices a razor-sharp zig-zag pattern into the surface water and suddenly the little five-inch flying fish has enough speed for another hop. Veering starboard to confound the mahi, she picks her tail up and is airborne once more. But the mahi isn't fooled; it turns with her and keeps on tracking. She'd hoped for better. She'd hoped it would take a greedy, premature swipe and in so doing shoot its proverbial bolt. It's not fooled, and she'll have to keep up the evasion. However many jumps she needs to coerce a reckless chomp. However many times it takes. On towards the horizon our combatants race, and only a splash in the distance gives away the mahi's final strike. Like the hero's fate in the classic short story "The Lady and the Tiger," the final outcome isn't for us to know.

The ocean guards its secrets well. Even a trait as conspicuous as speed gets hidden below the waves, consigned to a "fun facts" label on your shrink-wrapped marlin steak. For all the modern science's leaps, our knowledge of the marine world remains patchy and public awareness downright threadbare. Why should "they taste good" be the first and only thing most people know about tuna, instead of appreciating its 30-knot oceanic migrations? We look out to the ocean and see an empty watery expanse, when in fact continents' worth of life moves below. That we are learning these creatures' stories only now, in the age of depleted fisheries and changing climates, is a cruel irony. There is no time like the present to immerse ourselves in fascinating tales of marine science, to appreciate the extreme life of the sea for the guiltless wonder it is.

Stephen R. Palumbi is Professor of Biology and Director of the Hopkins Marine Station at Stanford University. Anthony R. Palumbi is a science writer and novelist whose work has appeared in the Atlantic and other publications. Together they are the authors of The Extreme Life of the Sea.