| Snake mackerel | |
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Scombriformes |
| Family: | Gempylidae |
| Genus: | Gempylus |
| Species: | G. serpens |
| Binomial name | |
| Gempylus serpens G. Cuvier, 1829 | |
| Synonyms | |
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Thesnake mackerel (Gempylus serpens) is the sole species of fish in the monotypic genusGempylus, belonging to the familyGempylidae (which is also referred to generally as "snake mackerels"). It is found worldwide intropical and subtropicaloceans between thelatitudes of42°N and40°S; adults are known to stray intotemperate waters. It is found to a depth of 600 meters (2,000 feet).[2] Populations of the snake mackerel from theAtlantic and theIndo-Pacific differ invertebral count (51–55 versus 48–50) and number of firstdorsal fin spines (30–32 versus 26–30), and so may represent separate species.[3]
The snake mackerel has a very long, slender, laterally compressed body. It has a long, pointedhead, measuring 17–18% of thestandard length, and a largemouth with thelower jaw protruding beyond theupper. Both jaws are densely packed with sharp teeth; the first few teeth in the upper jaw are enlarged into fangs. Thepectoral fins contain 12–15rays; thepelvic fins 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. Theanal fin 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 twolateral lines, with the upper running to the rear of the first dorsal fin and the lower running to thecaudal peduncle. The scales are mostly absent. The coloration is metallic brown, with dark fins. This species grows to 1 meter (3.3 feet) in length.[4][5]
Adult snake mackerels conduct adiel vertical migration, 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.[6] This species feeds onsquid, pelagiccrustaceans, andbony fishes such aslanternfishes,flying fishes,sauries, andmackerel.[5] It is in turn preyed upon bytuna andmarlin. There was an 80 cm long specimen found inside a deadblack swallower which measured 25 cm.[4] Reproduction isoviparous, with females producing 300,000 to 1,000,000eggs.[5]Spawning occurs year-round; spawning areas are known to exist in theCaribbean Sea and off the coast ofFlorida.[6] Males reachsexual maturity at 43 cm (17 in) long and females at 50 cm (20 in) long.[5] As the fish mature and move into deeper water where there is less available light, they lose thecone cells in their eyes in favor ofrod cells.[7]
The snake mackerel is caught asbycatch in the tunalonglinefishery and is of minor commercial importance. It is marketed frozen or insausages andfish cakes.[2][3] InHawaii, this fish is known ashāuliuli 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.[8] A night-time encounter withGempylus species in the open sea is described by Thor Heyerdahl in the accounts of theKon-Tiki expedition. 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 nightsGempylus was abroad high over the surface of the sea; we on the raft had experience of that".[9]
