FAO Species Identification Guide for Fishery Purposes Western

794 Cephalopods
Sthenoteuthis oualaniensis (Lesson, 1830)
Frequent synonyms / misidentifications:
Symplectoteuthis oualaniensis (Lesson, 1830) /
None.
FAO names: En - Purpleback flying squid;
Fr - Encornet bande violette; Sp - Pota cárdena.
Diagnostic characters: Mantle cylindrical, very
muscular, with abrupt caudal taper; fins large
rhombic, with fin angle 60 to 70°. Head large, only
slightly narrower than mantle. Mantle element of
T-shaped locking apparatus curved with an
anterior bifurcation, fused to funnel element
along the posterior third of the longitudinal groove.
Funnel groove with foveola and side pockets;
tetraserial suckers on the dactylus of the tentacular
club; medial manus sucker rings with 1 tooth in
each quadrant greatly enlarged, 5 to 7 subequal
teeth in between; carpal fixing apparatus
consisting of smooth-ringed suckers and knobs on
the tentacular stalk; 2 approximately equal-sized
light organs present between the intestine and ink
sac in larvae and juveniles, one anteriorly near the
anus and the other posteriorly; single, oval light
organ also present ventrally on each eye in larvae
and juveniles; large dorsal light organ may be
present in larger individuals anteriorly on the
mantle. Either left or right ventral arm (IV) hectocotylized
in mature males, 6 to 8 pairs of normal
suckers proximally, sucker stalks and bases lost
distally and pores developed in the thickened dorsal
and ventral protective membranes basally and
medially.
Size: Maximum mantle length for the large form
to about 300 mm in the area, commonly to about 200 mm mantle length (another larger form from the
northwestern Indian Ocean reaches 650 mm mantle length).
Habitat, biology, and fisheries: Adults generally occur only where bottom depth is greater than 200 m, larvae
and juveniles occur also in clear, shallower water including around coral reefs. The more abundant large form
with the dorsal light organ patch occurs in oceanic waters throughout the area, capable of extensive vertical
migrations but also found in surface waters day and night, occurs in small schools (about 30 individuals) of like
size. Males of the large form reach maturity at 110 mm mantle length, females at 180 mm mantle length but with
seasonal and geographic variability; spawning appears to be geographically widespread in continental slope
waters and occurring year-round;spawning migrations have been reported from around Taiwan Province of China.
Males of the small maturing form reach maturity at 90 mm mantle length and females at 130 mm mantle length,
spawning times and locations for this form unknown. Preys primarily upon small pelagic fishes and crustaceans,
cooperatively hunting with other school members. Supports local fisheries around Nansei Islands (Okinawa) and
Taiwan Province of China from Spring to Autumn, caught by hand jigging, mechanized jigging has been tried
around Okinawa and Fiji without success, used for human consumption and for bait for tuna.
Distribution: Tropical waters throughout the Indo-Pacific region, from Okinawa in the north to northern Australia and
from East Africa to the eastern central Pacific.
Remarks: S. oualaniensis as it is currently rec-
ognized includes 2 forms in the Western Central
Pacific, one with and the other without a large
dorsal light organ patch on the anterior mantle
in adults. The former reaches in excess of
300 mm mantle length while females of the
latter form reach maturity at less than 200 mm
mantle length. The dorsal light organ patch develops
in specimens from 65 mm mantle length
and is readily visible at 100 mm mantle length.
funnel
2 light
organs
mantle
intestine
internal view of
anterior ventral mantle
(after Wormuth, 1976)
funnel
cartilage
mantle
funnel cartilage fused
with mantle cartilage
?
?
?
arm III
sucker ring
dorsal view
dorsal
lightorgan
patch
(not
always
present)
tentacular club
sucker ring