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Emperor and Swordfish: Same Fish or Not?
The confusion between emperor fish and swordfish is one of the most common at the fish market, and there's an explanation. In Spain, legally, swordfish and emperor fish are the same fish : the official list of commercial names for fish species accepts both names for the same species, Xiphias gladius . What you buy as emperor fish is swordfish.
The difference lies in the biology. There is another distinct fish, the Luvarus imperialis , or emperor fish, which in some areas is also called the emperor fish and which the FAO classifies as a separate species. We'll tell you what type of fish each one is and how to tell them apart.
What is the Emperor Fish?
In Spain, "emperador" is the accepted commercial name for the swordfish ( Xiphias gladius ). This is reflected in the list of commercial names for fishery and aquaculture species from the Ministry of Agriculture, Fisheries and Food, which registers the species with the FAO code SWO under the name "swordfish or emperor." Therefore, when you see slices or fillets of emperor at the fishmonger's or in the freezer, you are seeing swordfish: it is the same animal with two valid names.
The other emperor fish is Luvarus imperialis , commonly known as the luvaro , which is its official designation (FAO code LVM ). It is a pelagic fish with a tall, oval, silvery body, reddish fins, and no sword. It lives in temperate and tropical waters of all oceans, including the Mediterranean. It feeds primarily on jellyfish and gelatinous plankton, is caught only occasionally, and rarely reaches the market. If you have ever heard the emperor fish referred to as a different species from the swordfish, this is the one they are referring to.
What is the Swordfish?
The swordfish , scientifically known as Xiphias gladius , is one of the large pelagic fish of our seas. It is easily recognizable by its long, sword-shaped bill , which it uses for hunting, and is one of the fastest fish in the ocean: it can reach speeds of up to 100 km/h. In Spain, it is sold as swordfish or emperor fish, and depending on the region, you may also hear it called espadarte, peix espasa, or aguja palá.
It lives in temperate and tropical waters of the Atlantic, Mediterranean, Indian, and Pacific Oceans. Its flesh is firm, pinkish-white, and has very few bones , making it ideal for grilling, barbecuing, baking, or stews. It is usually served in slices or fillets.
Nutritionally, it is a rich source of protein and Omega-3 fatty acids , although it should be consumed in moderation due to its mercury content , especially by pregnant women and young children. Fishing for it is regulated to preserve the species.
Comparison: Emperor vs. Swordfish
If we're talking about the fish you buy in Spain, there's no comparison: emperor fish and swordfish are the same product . Both are accepted trade names for Xiphias gladius , a bony, oily fish.
The comparison that does make sense is between the two species that share the name emperor : the swordfish and the luvaro. These are their differences:
Feature | swordfish or emperor | Luvaro (the "other" emperor) |
Scientific name | Xiphias gladius | Luvarus imperialis |
FAO Code | SWO | LVM |
Trade name accepted in Spain | swordfish or emperor | Luvaro |
Appearance | Long, sword-shaped beak, elongated body | Oval and tall body, without a sword, reddish fins |
Habitat | Temperate and tropical waters, including the Mediterranean | Temperate and tropical waters, including the Mediterranean |
Food | Fish and cephalopods | Jellyfish and gelatinous plankton |
Market presence | Common, fresh and frozen, sliced and loin | Occasional catch, almost never for sale |
In the kitchen | Grill, barbecue, oven and stews | Not for regular culinary use |
In short: at the fishmonger's, the supermarket, or a restaurant, emperor fish and swordfish are the same thing . The FAO's distinction between species affects one fish, the sloe, which you'll almost never find for sale.
Frequently Asked Questions about the Emperor and the Swordfish
Yes. In Spain, swordfish and emperor are two accepted commercial names for the same species, Xiphias gladius. Buying emperor is buying swordfish. The only distinct emperor is the snook (Luvarus imperialis), a species that the FAO classifies separately and which is rarely traded.
The swordfish (Xiphias gladius) is usually classified as an oily fish due to its fat and Omega-3 fatty acid content, although its flesh is pinkish-white and some tables classify it as semi-oily. It is a bony oily fish, like tuna or bonito.
Swordfish live in temperate and tropical waters of all oceans. The Spanish fleet catches them mainly in the Atlantic and the Mediterranean, primarily using surface longlines. Their fishing is regulated by minimum sizes and quotas to protect the species.
The Luvarus imperialis, or emperor fish, is a pelagic fish with an oval, silvery body and reddish fins, lacking a sword-like structure. It lives in temperate and tropical waters, including the Mediterranean. In some areas it is called the emperor fish, but its official commercial name in Spain is emperor fish (FAO code LVM). It is caught occasionally and almost never reaches the market.
