Swordfish
Xiphias gladius
Animal Type: Bony fish
Habitat: Open ocean
Diet: Carnivore
Special Feature: Long sword-like bill
Size: Can grow more than 10 feet long
About Swordfish
Swordfish are large predatory fish named for the long, flat bill that extends from the front of their heads. This impressive structure looks like a sword and can make up a large portion of the fish's total body length.
They are powerful swimmers that spend their lives traveling through the open ocean. Swordfish can be found in tropical, temperate, and sometimes colder waters around the world.
What Is the Sword For?
The swordfish's famous bill is not simply decoration. It is an important hunting tool.
Swordfish can slash their bills through schools of fish, injuring or stunning prey before turning around to eat it.
This allows them to attack groups of fast-moving fish without having to grab each one immediately.
Swordfish have special tissue near their eyes that helps warm their eyes and brain. This is especially useful when they dive into cold, deep water while hunting.
The Twilight Zone
Swordfish often dive into the Twilight Zone, also known as the Mesopelagic Zone. This layer extends from about 200 to 1,000 meters (656 to 3,280 feet) beneath the surface.
Only a small amount of sunlight reaches this depth. As you descend, the water becomes darker and colder.
There is not enough sunlight for photosynthesis throughout most of the Twilight Zone. Animals living here must hunt other animals or depend on food that falls from the waters above.
Swordfish do not remain permanently in the Twilight Zone. They often move between deeper and shallower water while searching for prey.
Daily Vertical Migration
Swordfish often change depth throughout the day. During daylight hours, they may dive hundreds of meters into darker, colder water.
At night, they may move closer to the ocean's surface as prey animals also rise toward shallower water.
This movement between ocean layers allows swordfish to follow their food across a huge vertical range.
What Do Swordfish Eat?
Swordfish are carnivorous predators. They eat many kinds of fish as well as squid and other cephalopods.
Their prey may include mackerel, herring, hake, lanternfish, squid, and other animals living in both surface and deeper waters.
Built for Speed
Swordfish have streamlined bodies that allow them to move quickly through the ocean.
Adult swordfish have smooth bodies with greatly reduced scales. Their strong tails provide the power needed for fast swimming and chasing prey.
Their pointed bill and narrow body also help reduce resistance as they move through the water.
A Fish Without Teeth?
Young swordfish have small teeth, but adult swordfish lose them as they mature.
Instead of relying on teeth to capture prey, adults use their speed and sword-like bills to injure or stun animals before swallowing them.
Where Are They Found?
Swordfish are found throughout the Atlantic, Pacific, and Indian Oceans.
They usually live far from shore in open water and can migrate across long distances as they search for food and suitable temperatures.
Because they can tolerate a wide range of temperatures, swordfish may travel between warm surface waters and much colder deep water.
Young Swordfish
Baby swordfish look surprisingly different from adults. When they first hatch, their distinctive sword has not fully developed.
As they grow, their jaws lengthen and their bodies gradually develop the streamlined shape of an adult swordfish.
Life Between Two Worlds
Swordfish are a great example of an animal that does not belong entirely to only one ocean layer.
They can hunt in the bright waters of the Sunlight Zone and descend hundreds of meters into the dim Twilight Zone. Their ability to travel between these environments allows them to follow prey throughout much of the upper ocean.