The snake mackerel (''Gempylus serpens'') is the sole species of fish in the monotypic genus ''Gempylus'', belonging to the family

Gempylidae The Gempylidae are a family of perciform fishes commonly known as snake mackerels or escolars. The family includes about 25 species. They are elongated fishes with a similar appearance to barracudas, having a long dorsal fin, usually with one or ...

(which is also referred to generally as "snake mackerels"). It is found worldwide in

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and subtropical

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

s between the

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

s of 42°N and 40°S; adults are known to stray into

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

waters. It is found to a depth of . Populations of the snake mackerel from the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

differ in

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

l count (51–55 versus 48–50) and number of first

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

spines (30–32 versus 26–30), and so may represent separate species.

Description

The snake mackerel has a very long, slender, laterally compressed body. It has a long, pointed

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...

, measuring 17–18% of the

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

, and a large

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

with the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

protruding beyond the upper. Both jaws are densely packed with sharp teeth; the first few teeth in the upper jaw are enlarged into fangs. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s contain 12–15

rays Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (gra ...

; the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are tiny and located beneath the pectorals, containing 1 small spine and 3–4 rays. There are two dorsal fins; the first is long and spiny, and is followed immediately by the second, which contains 1 tiny spine and 11–14 soft rays. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

originates opposite the second dorsal fin and consists of 2 free spines followed by 1 spine and 10–12 rays. The dorsal and anal fins are followed by 6–7 finlets. There are two

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

s, with the upper running to the rear of the first dorsal fin and the lower running to the

caudal peduncle Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The scales are mostly absent. The coloration is metallic brown, with dark fins. This species grows to in length.

Behaviour

Adult snake mackerels conduct a

diel vertical migration Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The word ''diel'' comes from the Latin ''dies'' day, and means a 24-h ...

, staying in deeper water during the day and rising to the surface at night to feed. The young and juveniles also migrate vertically but in the opposite direction, staying near the surface during the day and moving deeper at night. This species feeds on

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

, pelagic

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s, and

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

es such as

lanternfish Lanternfishes (or myctophids, from the Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represent ...

es,

flying fish The Exocoetidae are a family of marine fish in the order Beloniformes class Actinopterygii, known colloquially as flying fish or flying cod. About 64 species are grouped in seven to nine genera. While they cannot fly in the same way a bird do ...

es,

sauries Sauries are fish of the family Scomberesocidae. There are two genera, each containing two species. The name Scomberesocidae is derived from the ''scomber'', which in turn is derived from the Greek ''skombros'', meaning "mackerel", and the Latin ...

, and

mackerel Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. ...

. It is in turn preyed upon by

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max length: ...

and

marlin Marlins are fish from the family Istiophoridae, which includes about 10 species. A marlin has an elongated body, a spear-like snout or bill, and a long, rigid dorsal fin which extends forward to form a crest. Its common name is thought to deri ...

. There was an 80 cm long specimen found inside a dead black swallower which measured 25 cm. Reproduction is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

, with females producing 300,000 to 1,000,000

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

Spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...

occurs year-round; spawning areas are known to exist in the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

and off the coast of

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

. Males reach

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

at long and females at long. As the fish mature and move into deeper water where there is less available light, they lose the

cone cell Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cone ...

s in their eyes in favor of

rod cell Rod cells are photoreceptor cells in the retina of the eye that can function in lower light better than the other type of visual photoreceptor, cone cells. Rods are usually found concentrated at the outer edges of the retina and are used in per ...

Human interaction

The snake mackerel is caught as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

in the tuna

longline Long line or longline may refer to: *''Long Line'', an album by Peter Wolf *Long line (topology), or Alexandroff line, a topological space *Long line (telecommunications), a transmission line in a long-distance communications network *Longline fish ...

fishery Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

and is of minor commercial importance. It is marketed frozen or in

sausage A sausage is a type of meat product usually made from ground meat—often pork, beef, or poultry—along with salt, spices and other flavourings. Other ingredients, such as grains or breadcrumbs may be included as fillers or extenders. ...

s and

fish cake A fishcake (sometimes written as fish cake) is a culinary dish consisting of filleted fish or other seafood minced or ground, mixed with a starchy ingredient, and fried until golden. Asian-style fishcakes usually contain fish with salt, water, ...

s. In

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, this fish is known as ''hāuliuli'' and is considered good eating cooked or dried. King Kamehameha was apparently not fond of it, as he once remarked that it is a "delicious fish for the back country people", meaning fine for those who could not obtain anything better. A night-time encounter with ''Gempylus'' species in the open sea is described by Thor Heyerdahl in the accounts of the

Kon-Tiki expedition The ''Kon-Tiki'' expedition was a 1947 journey by raft across the Pacific Ocean from South America to the Polynesian islands, led by Norwegian explorer and writer Thor Heyerdahl. The raft was named ''Kon-Tiki'' after the Inca god Viracocha, for ...

. After a member of the raft expedition was awoken by a mysterious fish landing on his sleeping bag, the crew member caught a long thin fish that was "over three feet long, as slender as a snake, with dull black eyes and long snout with a greedy jaw full of long sharp teeth. The teeth were sharp as knives and could be folded back into the roof of the mouth to make way for what is swallowed." Later Thor Heyerdahl notes: "Only the skeleton of a fish like this one had been found a few times on the coast of South America and the Galapagos Islands; ichthyologists ... thought it lived at the bottom of the sea at a great depth, because no one had ever seen it alive. But if it lived at a great depth, this must at any rate be by day, when the sun blinded the big eyes. For on dark nights ''Gempylus'' was abroad high over the surface of the sea; we on the raft had experience of that".

References

{{Taxonbar, from=Q1817179 Gempylidae Fish described in 1829 Taxa named by Georges Cuvier