Author: (Cuvier, 1817)
Field Marks:
An unmistakable shark, with its immense, broad, wing-shaped head, nearly or quite half the shark's length.
Diagnostic Features:
Head wing- or arrow-shaped in dorsoventral view and very broad, width across head about 40 to 50% of total length; lateral blades of head very narrow and winglike; nostrils greatly enlarged, their widths 0.8 to 0.9 times in internarial width and nearly twice mouth width; bumps present along anterior margin of head opposite nostrils. Upper precaudal pit longitudinal and not crescentic.
Geographical Distribution:
Indo-West Pacific: The "Gulf" between the Arabian Peninsula and Iran to Pakistan, India, Sri Lanka, Bangladesh, Burma, Malaysia, Thailand, Viet Nam, China, Taiwan Island, The Philippines, Indonesia, Australia (Queensland and Northern Territory).
Habitat and Biology:
A rather small tropical shark of remarkable appearance, found in shallow water on the continental and insular shelves.
Viviparous, with a yolk-sac placenta; number of young 6 to 11 (most commonly 6). In Bombay waters, birth takes place just mating apparently takes place during the monsoon, June through August, and females with small embryos appear in September and October; this suggests a gestation period of about 8 months, but this needs to be confirmed. Pregnant females are said to fight each other.
The diet of this small shark is not reported, but it probably consists of small fishes, cephalopods and crustaceans. An apparently harmless shark, not known to attack people.
The function of the vast lateral blades of the head of this shark are uncertain; they seem excessively hypertrophied for manouvering organs or bowplanes, but perhaps more important is their role in increasing the volume and surface area of some of the sense organs of the head, particularly the lateral line canals, Ampullae of Lorenzini, and olfactory organs, as well as providing an increased stereoscopic visual effect.
Size:
Maximum possibly not exceeding 152 cm, males immature at 79 cm and adult at 132 cm, presumably maturing at a metre or less; pregnant females are 104 to 144 cm; size at birth 32 to 45 cm.
Interest to Fisheries:
A common fisheries species in India, Pakistan, Malaysia and Thailand, and probably elsewhere in its range. It is caught with floating gillnets, probably fixed bottom gillnets, stake nets, seines, with floating and bottom longlines, and probably on hook-and-line. Its meat is utilized fresh for human consumption; livers yield a high-potency vitamin oil; and offal is probably processed into fishmeal.
Remarks:
Cuvier (1817), in a footnote to his account of Squalus zygaena Linnaeus, 1758 (placed in the new subgenus Zygaena Cuvier, 1817, but listed as S. zygaena), described this species as follows: "(3) Ajoutez l’ espèce représentée par B1.117, reconnaissable à ses narines placées bien plus près du milieu (z. nob. Blochiil. Sa deuxieme dorsale est aussi bien plus près de la caudale" (ftn 3, p. 127). Cuvier's citation of this species may not be a properly formed Linnaean binomial, but apparently he intended to show that the Squalus zygaena Bloch, 1785 was not conspecific with S. zygaena Linnaeus, 1758. "z. nob. Blochii" can be interpreted as Zygaena Blochii nobis (that is of Cuvier, 1817), as was done by Valenciennes (1822), who had an alcohol-preserved specimen of the species and described and illustrated it in detail.
Type material:
Holotype: None? Fowler (1941) thought the type locality to be India.