Sword Fish - Facts

Sword Fish Facts

Swordfish, otherwise known as Xiphias Gladius is a species of bill fish. They are known for their easily identifiable sword like protrusion from their faces, which is used to slice at prey and make them easier to catch. 

They are the only member of the Xiphiidae family - although they do seem superficially similar to fish such as Marlin, sailfish they are in fact a different species. The difference between marlin, other billfish and Swordfish is the shape and texture of their bill. Marlins have a rougher rounded, shorter bill, and they also come in a variety of species.

The swordfish’s closest relative is Chinese sword fish or Psephurus Gladius (a sturgeon) which lives in fresh water and not salt water and has a much longer life-span.
The sword like protrusion of this species allows them makes short work of their favorite prey – squid, octopus & smaller pelagic fish, such as bluefish and mackerel - even in large numbers. Swordfish prefer 'pelagic' fish as they are the type of fish which are normally found in the upper region of the sea - not to close to reefs, or the ocean floor. Sword fish tend to swim in water depths of up to 2,100 feet, much deeper than other billfish such as Marlin.

The sword fish’s unique bill also puts it at a very high position on the food chain, with its only predators being killer whales, tuna, sharks and man.

At birth, the sword is not present, but rather a set of teeth are. Over time the teeth are lost and the 'sword' grows as the fish matures. They are also born with scales, which disappear by the time full maturity has been reached. Swordfish are considered fully mature at 4-5 years old. This is when they can begin reproduction. Mature females are considerably larger than males.

Swordfish reproduce by laying eggs, that is to say that they are oviparous. Female swordfish can lay anywhere between 1,000,000 and 30,000,000 eggs at one time and fertilization is internal. The mother lays zygote eggs and allows them to develop externally from her body.  It is a common method of reproduction for many fish.
Swordfish usually grow to be up to 10ft long and weigh 150-200lbs on average, although they have been noted to have grown to be up to 16ft long and weigh an incredible 1000+ lbs in rare cases.

Swordfish can be found slicing through the warmer waters of the Pacific, Atlantic and Indian oceans at high speeds. It's possible for them to reach high speeds when swimming as their sword can both help in swimming function and it breaks up the water around the fish allowing it to propel itself forward faster.

The reason that sword fish tend to stick to the warmer regions of water is a nearly negligible source of inner body heat regulation, meaning they can't keep themselves at the optimum temperature they need to survive naturally. They are ectothermic animals, which rely almost entirely on the environmental heat to stay alive.

This species prefers to be in water which is around 18-22 Celsius or the mid 60s to 70s Fahrenheit. Although they can and have ventured into colder waters as they can withstand a somewhat varied temperature range as they are a highly migratory species and they do not stay in a given area for particularly long. Unfortunately these mostly nocturnal fish do not tend to live for much longer than 10 years.

They are a commercially sought 'food fish' all over the world; the USA, Canada, Portugal, Brazil, Japan, Spain, Taiwan, and Uruguay all indulge in Sword fishing. Harpoons or fishing rods are prevalent tools used to catch sword fish as they are adept at using their 'swords' to cut through nets when trapped. Even when the harpoon method is used Swordfish are still extremely dangerous and put up fierce resistance. They often end up impaling their swords in the ocean floor or causing extreme damage to the boats with their swords.

It is commonly grilled and served with lemon as a dish and is very high in potassium, protein, omega 3 fatty acids, Vitamin D and many minerals.


The Encyclopedia of Animals; A Complete Visual Guide by Drs. Fred Cooke, Hugh Dingle, Stephen Hutchinson, George McKay, Richard Schodde, Noel Tait and Richard Vogt.

Weldon Owens Pty Ltd.

Posted on August 11, 2014 and filed under Saltwater Fish.