The snake mackerel ( Gempylus serpens) is the sole species of fish in the monotypic genus Gempylus, belonging to the family Gempylidae (which is also referred to generally as "snake mackerels"). It is found worldwide in tropical and subtropical between the of 42°N and 40°S; adults are known to stray into temperate waters. It is found to a depth of . (1993). 925103124X, Food and Agricultural Organization of the United Nations. 925103124X
Description
The snake mackerel has a very long, slender, laterally compressed body. It has a long, pointed
head, measuring 17–18% of the
standard length, and a large
mouth with the
lower jaw protruding beyond the
upper jaw. Both jaws are densely packed with sharp teeth; the first few teeth in the upper jaw are enlarged into fangs. The
contain 12–15
fin ray; the
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 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
, with the upper running to the rear of the first dorsal fin and the lower running to the
caudal peduncle. The scales are mostly absent. The coloration is metallic brown, with dark fins. This species grows to in length.
Peterson, R.T. (1999). 061800212X, Houghton Mifflin Harcourt. 061800212X
Behaviour
Adult snake mackerels conduct a diel 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.
This species feeds on
squid, pelagic
, and
such as
,
,
sauries, and
mackerel.
It is in turn preyed upon by
tuna and
marlin. There was an 80 cm long specimen found inside a dead
black swallower which measured 25 cm.
Reproduction is
oviparous, with females producing 300,000 to 1,000,000 eggs.
Spawning occurs year-round; spawning areas are known to exist in the
Caribbean Sea and off the coast of
Florida.
Males reach
sexual maturity at long and females at long.
As the fish mature and move into deeper water where there is less available light, they lose the
in their eyes in favor of
.
Human interaction
The snake mackerel is caught as
bycatch in the tuna
longline fishing fishery and is of minor commercial importance. It is marketed frozen or in
and
.
In
Hawaii, this fish is known as
hāuliuli and is considered good eating cooked or dried.
Kamehameha I 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. 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".
