Black Marlin, Istiompax indica
The Black Marlin, Istiompax indica, whose common Spanish name is marlin negro, is the largest fish within the family Istiophoridae, the Billfish, known as picudos in Mexico. This species changes color to white upon death giving rise to the alternative common and confusing name of “White Marlin”. Note: this fish has very recently been placed in the Istiompax genus having formerly been known as Makaira indica. Globally, there is only one species in the genus Istiompax, which is found in Mexican waters of the Pacific.
The Black Marlins have long robust but not strongly compressed bodies. They are dark blue dorsally and silver ventrally with a limited number of vertical stripes or spots on their sides. Their first dorsal fin is black to dark blue and their other fins are brown. Their head has a long stout upper bill with a rounded cross section and relatively small eyes. Their mouth is equipped with small rasp-like teeth on both jaws. They do not have gill rakers. They have two anal fins, the first with 10 to 14 rays and the second with 6 or 7 rays. They have two dorsal fins; the first being low, rounded, less than half the body depth in height, and featuring a long base and 34 to 43 rays; the second located before the second anal fin and featuring 5 to 7 rays. Their caudal fin is deeply forked. Their pectoral fins do not fold against the body, which is unique to this species. Their pelvic fins are shorter than the pectoral fins. There are two keels on the side of their tail base. Their lateral line is visible and curves over the pectoral fins and straight toward the tail base. Their body is covered with thick elongated bony scales.
The Black Marlins are an epipelagic and oceanic species usually found in surface waters above the thermocline and often near shore. They have also been found at depths up to 1,000 feet by satellite tagging. Scientifically they have been extensively studied. They are a seasonal migratory species traveling in schools and are only found in waters with temperatures between 21o and 28oC. Males and females are indistinguishable by external features. All trophy catches are females, as females are significantly larger than males; males do not exceed 300 pounds. The World Record was caught in Peruvian waters in 1952, measuring 4.42 meters (14 feet 6 inches) and weighing 709 kg (1,560 pounds), however, they normally range in size from 150 to 300 pounds. Being carnivorous and non-selective feeders, they compete for the same food as other billfish, dorados, large sharks, swordfish, large tuna, and wahoo. They stun their prey with their elongated bill and then circle back to collect them. Once mature they are generally free from predation by other fish. Reproduction is via pelagic eggs with each female capable of releasing up to 40 million eggs per annum. Juveniles are fast growing and seldom seen by humans. They are found in all Mexican waters of the Pacific with the exception of the extreme northern Sea of Cortez.
The Black Marlin is most likely confused with the Blue Marlin, Makaira nigricans (blue coloration; dorsal height less than body depth; gradated first dorsal fin).
The Black Marlins are a highly prized big game species and one of the true “BIG FISH” in the ocean. They are known for their phenomenal acrobatic aerial displays when hooked, their size and strong stamina. Commercially they are pursued by longlining, harpooning, trolled nets, and set nets with global annual catches on the order of 3,000 tons. The majority are caught are a by-catch of commercial longlines targeting tuna who use as many as 2,000 hooks in one string. The quality of the flesh is considered “good” and they are marketed fresh and frozen and utilized primarily for sashimi with a large market in Japan.
From a conservation perspective, their global population is not well documented and they are currently considered “data deficient”, noting that very limited global conservation measures have been put in place. However, they are protected in Mexico, where they cannot be taken commercially in a 50-mile coastal zone area.
A word of caution: these fish are ginormous wild animals and their spears are very dangerous!