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Romping with the Unicorns of the Sea

Text and photography by Doug Perrine


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picture of pelagic Atlantic sailfish, Istiophorus albicans or platypterus feeding on sardines that they have broken off from the small bait ball in background, Yucatan Peninsula, Mexico, Caribbean Sea, near Contoy Island, Isla Mujeres, Cozumel, Cancun Image #: 035912

As with all semi-mythic beasts, the lore of the sailfish consists of a bit of fact mixed with large portions of fantasy, conjecture, and hyperbole. Of its biology, relatively little is known. Is it one species, or two? Scientists are in disagreement. Some recognize both an Atlantic sailfish, Istiophorus albicans, and a Pacific variety, Istiophorus platypterus, while others consider all sailfish to belong to the latter species.

Sailfish belong to the family Istiophoridae, or billfishes, which includes eleven species of marlin, spearfish, and sailfish (ten if you only count one species of sailfish). The broadbill swordfish is in its own family, the Xiphiidae. In addition to their distinctive unicorn-like upper jaws, billfishes are notable for the circulatory adaptations which heat their brains and retinas above the temperature of the surrounding water. Sailfish are distinguished by having by far the most elongated first dorsal fin – an elaborate device which functions as both a rudder for controlling swimming direction and as a visual display. It can be quite stunning when the sail is “lit up” in purple with black spots. Sailfish tend to be more coastal than other billfishes, often hunting in fairly shallow water, and tend to stay in surface waters even in the pelagic zone. They are found worldwide in tropical to temperate waters in latitudes from the equator to as high as 50 degrees.

Is the sailfish the fastest animal in the ocean? This claim is widely repeated, with a maximum swimming speed of 68 mph often listed, without reference to the source of this measurement. Anybody even remotely familiar with the characteristics of water should have reason to be skeptical of such a claim. And the fact that both orcas (killer whales) and pseudorcas (false killer whales) are known to feed on sailfish should cause one to wonder if the fish could really be faster swimmers than the larger and warm-blooded mammals that prey on them.

It turns out that the calculation of 68 mph was based on the amount of line stripped off a fishing reel by a hooked sailfish that was leaping repeatedly during the three-second duration of the speed trial. Even allowing that it was moving through air, rather than water, and that there may have been some imprecision in the measurement, such a feat is impressive. Irrespective of the extreme difficulty of making accurate measurements of the swimming speed of any wild animal and the futility of attempting to compare them with estimates made by other methods, the sailfish is a superb athlete, capable of bursts of speed that leave a human totally helpless by comparison.

Also known as a “bayonet fish”, the sailfish is a mighty hunter armed with a defensive/ offensive weapon that can approach half the length of the rest of its body. Imagine a cheetah with a chain saw strapped to its nose and you get a rough idea of what that bill means to a sardine. The sword itself is, however, but a part of the unusual arsenal of anatomical and behavioral weaponry that make the sailfish one of the most formidable predators in the sea.

Although popularly conceived as lone hunters, sailfish in fact often travel and hunt in packs. Their social characteristics make them considerably more lethal to the small schooling fish and squid that make up the bulk of their prey. A cooperative hunting group is able to break off a portion of a large shoal of sardines, form it into a tightly packed bait ball, and keep it surrounded until every last sardine is consumed. The hunters control their prey by making quick turns and suddenly raising their sails – the most impressive first dorsal fin of any fish – while flashing colors across their body in a “shock and awe” display that has to be seen to be believed. Fishers refer to a billfish that is displaying its iridescent hunting coloration as being “lit up” because the blue lines, spots, and patches on the body and tail appear to glow. In fact they may be glowing, or more properly fluorescing. The tail especially may appear day-glo blue to the naked eye, but appear as white in photographs – a difference that often indicates that the observed color is fluorescent.

Any sardine that panics and attempts to bolt from the school is quickly chased down and killed, but staying in the bait ball only postpones the inevitable, as the sailfish take turns charging through the ball slashing with their bills then circling back to gobble up the stunned fish. Other prey found in the stomachs of sailfish include anchovies, mackerels, jacks, needlefish, dorado (also a predator of juvenile sailfish), puffers, boxfish, triggerfish, small tuna, and ribbonfish – a bizarre mid-ocean fish that is a distant relative of sailfish.

Their efficiency as hunters enables sailfish to achieve a growth rate that is nearly as phenomenal as their swimming speed. They can stretch from a length of 0.125 inches at hatching from the egg to a length of 4.5 feet in only six months. At this length the eel-like fish weighs only six pounds, but it begins to bulk up as its growth in length slows. At an age of two years the growth of males slows considerably, while females continue to grow, becoming considerably larger than the males, and reaching a maximum size of over eleven feet and 220 pounds.

Can that bayonet be used to menace a creature much larger than the sailfish’s prey, such as a human, perhaps? I pondered that question as I slipped into the inky water surrounding a University of Miami research vessel anchored at a depth of 200-300 feet off the Bahamas on a moonless night in the late 1980s. The ship’s lights had attracted a school of squid, which in turn had drawn in a white marlin to feed on them. By the time I got into the water the marlin had disappeared, but as I peered into the darkness surrounding the pool of light next to the ship, a sailfish appeared, lit up and swimming erratically, slashing its bill back and forth through the school of squid. I took one flash picture and the sailfish turned and charged me, striking my swim fin with its bill before turning and vanishing into the night. I was never sure if the sailfish had been able to see me in the darkness, especially after being blinded by my flash, and reasoned that it might have been confused.

Just how dangerous a confused and frightened sailfish can be was dramatically demonstrated in 1996 when a group of divers on a live-aboard trip in Thailand encountered a pod of false killer whales that was attacking a sailfish. Several divers entered the water on snorkel to witness the dramatic event. The panicked sailfish suddenly charged diver Margie Meier. She raised her leg to block the attack, but the fish drove its bill right through her thigh and into her abdomen, perforating her intestine. Only excellent first aid, an emergency evacuation, and immediate surgery saved the diver’s life.

The fish responsible for that trauma was, of course, caught in a desperate fight for its life, so its aggression is easily understood, but what about a billfish that is hunting its dinner, and suddenly faced with a similarly-sized creature that might appear as either a competitor or predator? This thought weighed heavily on my mind when Captain Anthony suggested that we drop into the water with our cameras while the crew of his sportfishing boat teased sailfish to the transom with hookless lures.

We were in the Mexican Caribbean – an area known for years to sportfishing enthusiasts as hosting perhaps the greatest seasonal concentration of sailfish in the world, but only revealed to the general public with the release of a BBC “Planet Earth” segment featuring Rick Rosenthal’s stunning footage of dozens of sailfish hammering a ball of sardines. Anthony cautioned us that Rick is not only a very talented cameraman, but had also been unusually lucky during that shoot, and that such a photographic opportunity would not be easy to come by again.

True to his word, day after day passed with no sight of bait on the surface. For days at a time we didn’t even set foot on the boat while the wind howled outside our hotel windows and the sea turned into a boiling cauldron of green peaks leaping up and disintegrating into white foam. On days when the weather gods smiled on us we trolled our teaser lures and watched for dark shapes materializing behind them. When that happened, the cry “pez vela!” (sailfish) rang out, and we took turns slipping into the water while Rogelio and Gayo cast baits from spinning rods and reeled them past us to draw the fish in. To our great relief, the well-armed predators either shied away from us or just ignored us in their frenzy to get the bait. While we often only saw one or two sailfish at the surface, when we got in we could usually see a school of up to a dozen others just below.

Finally one day, word crackled over the radio that the sails had corralled a ball of bait at the surface. We raced to the spot and waited for the fishing boats to give us a turn at the action. When we got the all clear and slipped into the water we were witness to a life-and-death struggle played out at maximum intensity. The sailfish were not able to establish tight enough control of the baitball to hold it in place, so the sardines were racing away as fast as they could move while maintaining their defensive formation. Only ten to twenty sailfish were actively herding the sardines and taking turns feeding on them, but dozens more were trailing along behind and below. Any sardine forced out of the ball immediately had one or more sailfish hot on its tail with no chance of escape. However, as we soon discovered, a five-inch fish swimming for its life can easily outsprint a photographer equipped with the latest high-tech fins. We needed repeated boat drops to keep us near the action, but were never able to quite get in the middle of it. Even our oxygen-starved brains had to acknowledge that the lactic acid build-up in our legs was reaching critical levels by the time we got the call that it was time for a fishing boat to take its turn. A few minutes later the bait either dove or was completely consumed and we were once again staring out over an empty sea, wondering if the whole wild melee had been some kind of mirage or hallucination. Had we really been in the water with close to a hundred swimming rockets with front-mounted bayonets slashing a tribe of small helpless creatures to oblivion? We had cursed our bulky camera housings as we pushed them through the water, but now they contained the only evidence of the carnage we had seen.