---
title: "Swordfish (Xiphias gladius) | AnimalTracks.wiki"
description: "A fish with a heater for its brain and a flattened bill it apparently uses to slash prey."
image: "https://animaltracks.wiki/images/animals/swordfish-1.webp"
published: "2026-10-09"
updated: "2026-10-09"
---
# Swordfish (*Xiphias gladius*)
> **Status**: Checked against 4 sources, listed under Sources below.
> **Tagline**: A fish with a heater for its brain and a flattened bill it apparently uses to slash prey.
> **Soundtrack Vibe**: Drum & Bass / Precision Jungle // Squarepusher, "Squarepusher Theme"
> **Soundtrack Links**: [Spotify](https://open.spotify.com/track/5A8mxgppIz71mCLz7xAhpn)
> **Vibe Match**: A swordfish's warmed eyes can resolve rapid motion more than ten times better than fish eyes at water temperature, depending on dive depth. Squarepusher's breakbeats are cut into rolls and fills too quick to count, built for ears that keep up with fast motion.
## Biological Superpowers & Stats
- **Taxonomy**: *Xiphias gladius*
- **Danger Level**: Low
- **Conservation Status**: Near Threatened ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2022-1.rlts.t23148a46625751.en))
- **Superpower**: A heating tissue in one of its eye muscles that warms the brain and eyes up to 10 to 15 degrees C above the water, one adaptation that lets it swim in depths where the water may be just above freezing
- **Habitat**: Open oceans worldwide, in tropical, temperate and sometimes cold waters
- **Diet**: Mostly pelagic fish, and some squid
- **Tags**: fish, ocean, pelagic, deep-diver, predator, carnivore, migratory
## Natural History & Behavior
## A heater for the brain
Swordfish are believed to swim down to 2,100 feet (650 m) or deeper, where the water may be just above freezing. One adaptation that lets them swim in such cold water is a "brain heater": a large bundle of tissue associated with one of the eye muscles. It warms the eyes and brain up to 10 to 15 degrees C above the water around them.
One study showed that in fast-swimming predatory fish such as the swordfish, warming the retina improves temporal resolution, and so the detection of rapid motion. Depending on dive depth, it can be more than ten times higher in these fish than in fishes whose eyes match the water temperature.
> **Eggs by the million** A female swordfish may carry from 1 million to 29 million eggs, and estimates vary a lot.
## The sword
The bill is long, even for a billfish, and in cross section it appears as a flattened oval. Adults have no teeth and no scales. Young swordfish have scales, but they lose them by about 3 feet (1 m) long. Swordfish feed mostly on pelagic fishes (fish of the open sea) and occasionally on squid.
The sword is apparently used to catch prey. Squid and cuttlefish pulled from swordfish stomachs often carry slashes, and in one study most large fish prey had been slashed, while small prey were eaten whole.
## Size and lifespan
Swordfish reach a maximum of 177 inches (455 cm) and 1,400 pounds (650 kg). Nearly all of those over 300 pounds (140 kg) are female. The ones caught by the North Atlantic fishery average 50 to 200 pounds, and NOAA says North Atlantic swordfish live about 9 years. Females there can reproduce between 4 and 5 years of age.
Predators of adult swordfish include killer whales. Swordfish also host 49 species of parasites, from tapeworms in the gut to flukes on the gills.
## Where they roam
Swordfish live in the Atlantic, Pacific and Indian Oceans, from about 60 degrees north to 45 degrees south. They migrate, generally moving to warmer water in winter and cooler water in summer, and they often turn up in frontal zones, where ocean currents collide and productivity is high.
## Frequently Asked Questions
### Can a swordfish live in cold water?
Yes. Of all the billfish, the swordfish has the widest temperature tolerance, and it turns up in water from 41 to 80 degrees F (5 to 27 degrees C). It is mainly a warm-water fish, but its brain heater helps it swim in cold depths. *(Source: [Florida Museum of Natural History, Discover Fishes]())*
### How fast can a swordfish swim?
NOAA calls Atlantic swordfish one of the fastest predators in the ocean and says their streamlined bodies let them swim at speeds of up to 50 mph. *(Source: [NOAA Fisheries]())*
### Is the swordfish endangered?
The IUCN Red List rates the swordfish Near Threatened, which is a different category from Endangered. *(Source: [Collette et al. 2022]())*
## Sources
1. [Collette et al. (2022). Xiphias gladius. The IUCN Red List of Threatened Species 2022: e.T23148A46625751.]()
2. [Swordfish (Xiphias gladius). Florida Museum of Natural History, Discover Fishes.]()
3. [North Atlantic Swordfish. NOAA Fisheries.]()
4. [Fritsches, Brill & Warrant (2005). Warm eyes provide superior vision in swordfishes. Current Biology.]()
*Published October 9, 2026. Last updated October 9, 2026.*
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