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Today on Animal Fact Files we’re talking about marlins or swordfish or sailfish or… billfish - seriously did you all know these are different fish?! Apparently this and this are not the same thing, and I legitimately had no idea. My dad might be an excellent angler, but that was definitely not passed down to me. He’s probably giggling about this right now. Anyway, because I had no idea these are different fish, this seemed like a good opportunity to make sure I’m not the only one walking around making this egregious mistake.

The broad term for fish that generally look like this is billfish… or marlin. Some are commonly called “marlin” like black and blue marlins; there are also sailfish… who are also considered marlins but they’re commonly called sailfish; there are also spearfish - still marlins but most commonly known as spearfish. And, though this looks like a marlin - it isn’t. This is a swordfish which is sometimes called a broadbill. It superficially looks like marlins and other billfish but technically the swordfish isn’t related to them, so it’s usually classified in its own family.

Though swordfish and marlins look really similar, there are some key differences between these two groups of fish. There are currently eleven living species of marlins while there is only one living species of swordfish. A swordfish dorsal fin looks kind of like a shark fin while the dorsal fin of a marlin flows along the fish’s back giving it a sail-like appearance. The bill of a swordfish is flat and sword-shaped while the bill of a marlin is round and tends to be shorter than the bill of a swordfish. After reaching their adult size, which is more than three feet (1 meter) in length, swordfish no longer have teeth in their jaws or scales, but marlins have small teeth and scales present. Swordfish don’t have pelvic fins, and they tend to be more round than elongate bodied marlins.

Of course, it wouldn’t be easy to confuse these two groups of fish if there weren’t also similarities between them. Obviously both swordfish and marlins have a bill. Many people assume the bill is used to spear prey, but these fish actually use their bills to whack fish with a sideways smack, thus stunning the prey long enough to be eaten. Both swordfish and marlins eat mostly other fish but they take cephalopods, too. These fish are also similar in size. Swordfish have been recorded to reach nearly 15 feet (4.6 meters) in length and 1,400 pounds (635 kilograms) in weight while marlins can reach more than 12 feet (3.7 meters) in length and 1,500 pounds (680 kilograms) in weight (though it should be noted that some marlin species, like white marlins don’t get nearly as big). Because of this, these fish are considered some of the world’s best game fish and their meat can fetch high prices! Other predators to marlins and swordfish include killer whales, sharks, tuna, and even each other. These fish can also live to be more than ten years old!

Swordfish are found in marine waters worldwide with the exception of polar regions and marlins, though spread in different geographic areas depending on the species, tend to occupy this same expanse. These fish are oceanic fish, meaning they tend to be found in open water, but they may also inhabitat coastal areas, too. Swordfish tend to swim in deeper waters than marlins, but they can also be found along the surface. Both of these fish groups spawn in warm water and even migrate to find these optimal temperatures.

So, just to be clear - a swordfish looks like a marlin but isn’t; spearfish and sailfish are marlins, and marlins are also known as billfish.

For more facts on marlins, or billfish, or swordfish check out the links in the description. Thank you to Smiles and absentfish for today’s request! Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.