Few creatures are such masters of their natural element. Black marlin hear low-frequency vibrations, and while they may not have a highly developed sense of smell, the fish do have excellent vision. And they are fast. Black marlin may be capable of burst swimming at speeds of over 60 miles per hour. Their predators — apart from each other — include mako sharks, which may reach speeds of more than 35 miles per hour.
The tool of their trade is, as with other billfish, the outrageously elongated bone of the upper jaw, or "bill." The appendage likely evolved, says Pepperell, as a matter of streamlining and reducing friction. "The bill pierces the water, initiating smooth water flow over the body."
But the marlin also uses its bill to bat or ram its prey. Glassell's fish would have been able to bat around a big dolphin with its four-foot-long bill, as reported of another marlin by S. Kip Farrington in 1937. According to another observer, a marlin secures its prey by "rearing back its bill like a club and dealing it a hearty swipe, then watches its stunned prey as it slows its pace, flies into a flurry to face the marlin's massive jaws where it is swallowed whole."
Black marlin also use their rapiers to spear their prey, no matter what the size. Zane Grey found a snapper in a marlin's stomach with a hole straight through its body. A Bureau of Commercial Fisheries research vessel discovered a twice-speared 156-pound yellowfin tuna in the stomach of a 1,500-pound black marlin captured south of the Hawaiian Islands.
Since the days of the Greeks and Romans the swords of billfish have caused consternation and fear in humans because of the fishes' reputed proclivity to ram, attack and even sink ships. In an account from 1618 the Dutch explorer Willem Schouten, on a voyage around the world, noted in the log: "...there was such a noyse in the Bough of our Shippe....[The master] looked out over the side of the Ship hee saw the Sea all red...knowing not what it meant...." Back in port, Schouten reported, "Wee found a Horne sticking in the Ship, much like for thicknesse...a common Elephants tooth...." The "hard Bone" went through three planks and turned upward "...to our great good fortune, for if it had entred between the Ribbes, it would happily have made a greater Hole and have brought both Ship and men in danger to be lost."
No one knows how many black marlin thrive in the oceans of the world today. Says Pepperell, "All we know is, as many as 40,000 are taken in the Central and Western Pacific. We don't know if that is sustainable or if the catch is increasing dramatically. The reporting of catches has dropped off because long-liner fishermen are nervous."
The black marlin's range includes the Pacific and Indian oceans and occasionally the South Atlantic. Once the mighty marlin may have even considered New England's Georges Bank as an appropriate place to stop and have a meal, as noted in George Brown Goode's account in the report of the Commissioner of Fish and Fisheries circa 1880. Goode got his information from the interviews of one John H. Thomson of New Bedford, who reported earlier in the 19th century, "Of late years another school has appeared southeast of Cape Cod and George's banks about the 1st of August." Said Thomson, "These fish are altogether different [from the local billfish], being much larger, weighing from 300 to 800 pounds gross, and are entirely black."
Known spawning areas are few — the Great Barrier Reef, perhaps the South China Sea, maybe off the coast of Africa. Despite the many large females caught there, Cabo Blanco, Peru, was never noted as a spawning area, says Pepperell.
Now in the name of conservation, sport fishermen, charter boat captains and biologists are working together to promote tagging black marlin instead of killing them. Says Pepperell, some 30,000 have been tagged with a survival rate of 85 percent. Tagged marlin have now been known to cross 10,000 miles of ocean, notably from Australia to Baja California.
Tagging a black marlin poses somewhat different problems than, say, banding a bird. It's all done by darting. "Also, we have to keep the boat moving so the fish can breath," says Pepperell. "But when we let them go, the feeling on board that boat is just wonderful. Fishermen love and respect that big fish."