The larval fish look completely different from the adults. They grow for as long as they live, which may be for decades once they reach an intimidating size. Glassell's black marlin is thought to be 30 years of age. But aging a black marlin is guesswork. It's not as if you can cut off its bill and count the rings.
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. 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.