Swordfish are also know as "billfish." The word Gladius is related to the word gladiator. Swordfish are known as the gladiator because of their sharp, sword-like bill, which they use as a weapon. They will often encircle a group of fish, then charging through, they use their long snout as a spear, catching a meal. They are large, migratory predators found all around the marine ecosystem.  Swordfish are the only member of their family, Xiphiidae. The shortfin mako shark is one of the only creatures big and fast enough to chase down and kill a swordfish.  Swordfish have few predators as adults, but young swordfish are very vulnerable. Due to the high demand for Swordfish in cooking, the animal is becoming endangered.
The Swordfish has a relatively stout and round body. They reach a maximum size of 14 ft and 1,190 lbs. Males that grow to wiegh over 300 lbs. are rare. The Swordfish's snout, from which it gets its name, is long and sword shaped, and makes up one-third of its body. It will use this snout for catching prey and defending itself when useful. The Swordfish has two dorsal (topside) fins, the first of which is much larger than the second. It also has 2 anal fins, which resemble the dorsal fins. The Swordfish does not have any ventral (underside, belly) fins. Fully grown swordfish do not have scales or teeth. Baby Swordfish have thin, snake-like bodies. They have scales, and a single long dorsal fin, as well as a single anal fin.  Swordfish are cold-blooded, but have unique organs near their eyes that heat their eyes and their brain. The heating of the Swordfish's eyes improves their vision a good deal, and improves their ability to catch prey.  Swordfish are big fish. The average Swordfish weighs between 180 and 300 lbs. The biggest Swordfish caught, was about 550 lbs. Bigger Swordfish average a length of about 15 feet.  Marlins are also in the group Billfish.
Swordfish have been observed spawning in the Atlantic Ocean. Males and females pair up during their spawning season. Spawning takes place all year long in the Caribbean Sea, Gulf of Mexico, and the Florida coast. The most common spawning area is in the Mediterranean Sea. Female Swordfish are estimated to carry from 1 to 29 million eggs in their gonads. The height of their spawning occurs in July and August.The eggs are buoyant and are 1.6-1.8mm in diameter. Embryonic development takes place during the 2 ½ days following fertilization. As Swordfish grow, their body narrows.  A Swordfish reaches sexual maturity near 2 to 3 years of age. An adult swordfish diet includes small tuna, dorado, barracuda, flying fish, mackerel, as well as hake and rockfish, and squid.
Swordfish are found all across the Atlantic Ocean. They range from Canada, Argentina, and Ireland to South Africa. They are also found in the Indian Ocean and Pacific Ocean. Swordfish have been observed swimming in waters who's temperature was measured to be 10 to 15 C° above the surrounding water. Swordfish are most commonly found in temperate or tropical waters. They normally migrate between colder waters in the summer to warmer waters in the winter for reproduction.
The countries that bring in the most amount of swordfish catches are Spain, the United States, Canada, Portugal and Japan. Swordfish was a very popluar fish around World War II, until it was found to contain mercury. It made a rebound and is once again popular today. It is recommended that you do not restrict your diet to Swordfish, or consume large amounts of Swordfish. This is a precaution due to the levels of mercury found in Swordfish.
- Swordfish by Wikipedia
- Atlantic Swordfish Overview by NOAA
- Swordfish Rhode Island Sea Grant Fact Sheet