Istiompax indica was previously known as Makaira indica, and commonly known as the black marlin, is an oceanic species and one of the largest bony fishes in the world. They have a wide-ranging diet, undergo rapid growth and are known to have high fecundity. Females are usually bigger in size than the males but cannot be distinguished by their solely external features. They have an elongate body of a dark blue colour with silver undersides and a stout bill. The blue marlin is similar in appearance, but its pectoral fins can be depressed.
The black marlins are top predators, feeding mainly on fish and cephalopods (for example, octopus and squid). They are a highly migratory species and can commonly be found in the subtropical regions of the Pacific and Indian Oceans. Some individuals have been reported to migrate into temperate waters, such as that of the Atlantic Ocean but no breeding grounds can be found there.
The Black marlin has been listed under the data deficient category of the IUCN. The major threats to their abundance are commercial and recreational fishing. They are also caught as by-catch, especially during tuna longline fishery. As a top predator, billfish influence marine ecosystems and food webs, which will be inevitably altered if their population is not maintained at a stable density.
The Black marlin usually has a lifespan of nine to twelve years.
The Black marlin might be the fastest swimmer of the ocean.
Billfish are extremely visual predators, possibly possessing the ability to see in colour.