What Kind of Fish is Swordfish? A Detailed Look at This Unique Predator of the Sea
Swordfish are one of the most iconic and unique fish that inhabit our oceans. With their distinguishing elongated flat bill that resembles a sword, it’s easy to see where they get their common name. Swordfish have captured people’s imaginations for centuries yet many don’t know much about what kind of fish they really are. In this article, we’ll take a closer look at the biology, behavior, habitat, and uniqueness of the mighty swordfish.
To start, swordfish taxonomically belong to the family Xiphiidae which contains only one genus, Xiphias. Within this genus, there are two recognized species – the Atlantic swordfish (Xiphias gladius) and the Indo-Pacific swordfish (Xiphias platypterus) The Atlantic swordfish is found worldwide in tropical, subtropical and temperate waters of the Atlantic, Indian and Pacific Oceans whereas the Indo-Pacific swordfish is limited to the Indian and Pacific Oceans For this article, we’ll focus on the Atlantic Swordfish which is the species most commercially fished and consumed.
In terms of physical characteristics, swordfish are easily identifiable by their signature flattened, sword-like bill. This extended snout is used to slash at and stun prey during feeding. They also have a rounded torso, large eyes, and a tall, curved first dorsal fin. Swordfish are counter-shaded with a metallic dark blue to brown color on the dorsal side that fades to a white ventral side. This coloration helps provide camouflage when viewed from above and below in the water column.
One of the most remarkable features of swordfish is their large size. They are apex predators and the largest members of the billfish family Xiphiidae. Atlantic swordfish commonly reach sizes of 9 feet and weights up to 1,100 pounds. The all-tackle world record is a mammoth 1,182 pound fish caught off Chile in 1953.
Swordfish exhibit extremely fast growth compared to most fish species. After hatching, young swordfish grow about an inch per week. They reach sexual maturity relatively quickly at around 5 years of age and a weight of 200 pounds. Their rapid growth is aided by a metabolism and circulatory system adapted for fast swimming and hunting. Swordfish are able to thermoregulate, maintaining a body temperature up to 10°C warmer than the surrounding water. This allows them to swim and hunt in deep, cold water temperatures other fish can’t tolerate.
Speaking of hunting, swordfish possess incredible speed and agility to catch their prey. They are capable of burst swimming speeds up to 60 mph thanks to their rigid, streamlined bodies and specialized muscle structure. This speed makes them one of the fastest fish in the ocean. Swordfish primarily feed on a variety of fish like mackerel, herring, and hake. They also eat cephalopods including squid and octopus which can comprise up to 50% of their diet. They hunt using their extremely sharp bill to slash and stun prey. Their large eyes and specialized brain structure also give them excellent vision for detecting prey.
Swordfish roam all depths of the water column from the surface down to depths of 2000 feet, hunting for food. They undertake extensive seasonal migrations across thousands of miles from temperate feeding grounds to tropical spawning grounds. In the western Atlantic, swordfish migrate north in summer to feeding grounds on the Grand Banks off Newfoundland and south to warmer waters like the Gulf of Mexico in winter to spawn.
One unique aspect about swordfish reproduction is the fact that they exhibit asynchronous development, meaning they produce eggs on a continuous basis, not synchronized ovarian development. Spawning happens year-round in warm waters above 70°F, with peaks from November to March. During these peak spawning times, a single large female can produce tens of millions of eggs.
When it comes to conservation, swordfish were extensively overfished back in the 1990s. Since then, strict management measures have been put in place through NOAA Fisheries and other international bodies. Here in the U.S., North Atlantic swordfish are now considered rebuilt and not overfished thanks to science-based catch limits and careful monitoring.
From their torpedo-shaped build, warm-blooded circulation, incredible speed and migratory habits, swordfish are truly one of the most unique and specialized marine predators. Their iconic “sword” and large size has captured the imagination of people for centuries. So next time you order a nice swordfish steak, you can appreciate it as not just a tasty meal, but an opportunity to savor one of the most remarkable fish in the sea.
Quick Facts Region New England/Mid-Atlantic, Southeast
Swordfish swimming. Credit: Shutterstock/Joe Flynn
U. S. North Atlantic swordfish caught in the wild is a good choice for seafood because it is managed in a way that doesn’t harm the environment and is legally caught under U.S. S. regulations.
The stock is not overfished.
Not subject to overfishing.
Pelagic longline gear and handgear used to catch swordfish have no impact on habitat.
Regulations are in place to minimize bycatch.
- The 2017 stock assessment says that the North Atlantic swordfish is not overfished and will not be overfished in the future. Summary stock assessment information can be found on Stock SMART.
- ICCAT, the International Commission for the Conservation of Atlantic Tunas, keeps track of how many swordfish are in the Atlantic.
- Their name comes from their long, flattened bill that looks like a sword.
- They have a stout, rounded body and large eyes.
- Their first dorsal (back) fin is tall and crescent-shaped. Their second dorsal fin is much smaller.
- Their belly fins, called anal fins, look like their back fins but are smaller.
- They have a broad, crescent-shaped tail.
- Most of the time, they are black or brown on top and a lighter color below.
- One of the fastest fish that hunt in the ocean is the Atlantic swordfish. Because their bodies are smooth, they can swim very fast, up to 50 mph.
- Their largest size is about 1,165 pounds, and they grow very quickly. But most of the fish caught are between 50 and 200 pounds.
- Swordfish live about 9 years.
- Between the ages of 4 and 5, females can have babies. Females can lay anywhere from 1 million to 29 million eggs, depending on how big they are.
- In warm tropical and subtropical waters, they spawn more than once a year.
- From December to March, they spawn south of the Sargasso Sea in the western North Atlantic. From April to August, they spawn off the southeast coast of the United States.
- Swordfish eat many different kinds of fish and bugs, like squid.
- They catch prey by cutting it with their bill back and forth, which stuns or hurts the prey.
- Many things about them are unique, like the way their eyes work and how they exchange heat, which lets them hunt in deep, cold water.
- They are at the top of the food chain and are rarely eaten by other animals. Sharks and larger predatory fishes may sometimes eat juvenile swordfish.
| Kingdom | Animalia | Phylum | Chordata | Class | Actinopterygii | Order | Istiophoriformes | Family | Xiphiidae | Genus | Xiphias | Species | gladius |
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Is North Atlantic Swordfish Sustainable?
U. S. North Atlantic swordfish caught in the wild is a good choice for seafood because it is managed in a way that doesn’t harm the environment and is legally caught under U.S. S. regulations.
Year-round, with peaks from June through October.
U.S. wild-caught from U.S. Atlantic and Gulf of Mexico waters.
Moist and flavorful with a slightly sweet taste.
Firm with moderate oil content.
Raw flesh ranges from white and ivory to pink and orange. Cooked meat is beige.
Swordfish is an excellent source of selenium, niacin, vitamin B12, and zinc.