Difference Between Swordfish and Marlin

Swordfish vs Marlin

Swordfish and marlin are two very closely resembling large fishes, yet there many differences between them. Their characteristic shape with a sword-like snout and large body make them unique among all the marine creatures. This article intends to discuss the most important differences between swordfish and marlin with regard to their body sizes, fins, body shapes, colouration patterns, and taxonomic diversity.


Swordfish is a large migratory fish with a characteristically shaped snout or bill. It is scientifically known as Xiphias gladius, belong to the     Family: Xiphiidae of Order: Perciformes, and there is only one species of swordfish in the world. Broadbill is another common name to refer the swordfish in some areas, which is primarily due to the characteristic shape of their bill.

Swordfish is usually three metres long, but some individuals reach more than four metres in length. It is not a laterally flattened body but round-shaped. The weight ranges usually around 500 – 650 kilograms for an adult. The males are smaller and lighter than females, which is very common among fishes. These predatory fish can swim fast and are highly migratory. Their dorsal fin looks like a shark fin, and the pectoral fins are extended below the body. Swordfish is an ectothermic, but they have a network of capillaries that keep the eyes heated when the ambient temperature is as low as 10 0C. Thus, they have an improved vision to facilitate efficient predation.

Swordfish can inhabit a range of habitats from surface to deep waters of both temperate and tropical seas. Their distribution could be described as worldwide, as they are found in Indian, Pacific, and Atlantic oceans. However, there are some alterations in their body sizes between the populations found in different parts of the world. Swordfish can start sexual reproduction when they are 4-5 years old and live about nine years in wild.


Marlins are a group of large-bodied marine fishes with a large spear-like bill. There are about ten species of marlins described under three genera known as Istiophorus, Makaira, and Tetrapturus. They belong to the Family: Istiophoridae of the Order: Perciformes.

Depending on the species, marlins reach different body sizes ranging around 5 – 6 metres of length and 600 – 800 kilograms of weights. It is important to notice the tubular shape of their body, as it narrows only a little towards the posterior end. Most of the marlin species have vertical stripes on their body that could be used to identify them except the black marlins. Their dorsal fin is directed upwards, pointed, and runs backwards along the dorsal edge up to more than 80 % of the body length. The pectoral fins cannot be conspicuously observed due to their large body size. Despite their large body size, marlins are exceptionally agile swimmers with speeds up to 110 kilometres per hour.

Marlins are long-lived animals with lifespans of more than 25 years in wild, and they reach the sexual maturity at two to four years of age.

What is the difference between Swordfish and Marlin?

• Swordfish belong to the Family: Xiphiidae while marlins belong to Family: Istiophoridae.

• Swordfish is a single species whereas there are eleven species of marlins.

• Marlins are larger and heavier than swordfishes.

• The bill of swordfish is flat and pointed, while it is much like an arrow in marlins.

• Marlins can swim faster than swordfish.

• Dorsal fin is directed upwards in marlins, and it is directed backwards in swordfish.

• Dorsal fin runs along the back of marlins for the most parts but not in swordfish.

• Marlins have colouration patterns of vertical stripes but not in swordfish.

• Marlin’s body is more tubular than swordfish.

• Swordfish reach sexual maturity at 4-6 years of age but marlins become reproducible in 2-4 years from birth.

• Marlins live much longer in wild than swordfish does.