Knifetooth SawfishAnoxypristis cuspidata
Although sawfish look similar to sharks, they are very modified rays. The 'teeth' on their snout are actually specialize denticles, which are usually tiny protrusions on their skin that in this case, are enlarged and line their rostrum (snout). This particular sawfish lives along the sandy bottoms of the inshore ocean, sometimes venturing into estuaries and up rivers, and it is notably different than other sawfish because it lacks rostrum teeth closer to its head. They do have real teeth in their mouths; they use their toothy rostrum to stun prey before eating it.
Order - Pristiformes
Family - Pristidae
Genus - Anoxypristis
Species - cuspidata
Common names for the knifetooth sawfish include narrow sawfish, pointed sawfish, and pointed saw-fish. Non-English vernaculars referring to the knifetooth sawfish include: abusef (Arabic), beroi, cucut gergaji, kan sua, pamprang, parangpang, pemprang, prompran, yu gergaji, yu parang, and yu todak (Malay), billi sovulu (Kannada), chakku thatte (kannada), chhurio (Gujarati), cucut krakas, mungsing prampang, pamprang, parangpang, pemprang, and prompran (Javanese), hachutti meenu (Telugu), iluppa (Tamil), karati hangar (Bangladesh dialect), knivtandet savrokke (Danish), makara sravu, makarasravu (Malayalam), mestandzaagrog (Dutch), naithatte (Kannada), nali (Marathi), nokogiri-ei (Japanese), pez espada (Spanish), sayyafah (Arabic), shinavale (Marathi), shinesi (Telugu), vala sravu (Malayalam), veher (Gujarati), vela (Tamil), velli sravi (Malayalam), and win (Marathi).
Importance to HumansMost landings of the knifetooth sawfish are accidental, as they are caught in various net fisheries. These fish are sometimes targeted in artisanal net fisheries, hook and line fisheries, and can be harpooned or speared. Knifetooth sawfish are utilized in some areas as meat for human consumption, their fins are sold into the Asian 'shark fin' market, their livers are processed for oil, and their skins are made into leather. In addition, their rostra are used in traditional medicine, as religious offerings, and sold as curios. This species is used as food in parts of Asia, but is not known to be utilized as food in Australia. When this species is captured by Australian shrimp trawlers, their rostra are often removed and sold into the curio trade.
Danger to Humans
This species, like all sawfishes, is harmless to humans if left undisturbed. Humans are too large to be viewed as potential prey. Care must be taken when handling or approaching a sawfish of any size, as they may defend themselves when they feel threatened, using their rostrum to strike from side to side with considerable force.
The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.
Presently, no effective legislation exists to properly protect this species. Preliminary data indicates that adult knifetooth sawfish measure only about two-thirds of their former maximum size in Australian, although the species remains common. A major threat to this species is accidental capture in widely employed net fisheries throughout much of its range. In addition, it is vulnerable to near-shore hook and line fisheries in areas where this species is landed. Human-induced habitat loss and pollution of inshore coastal waters, estuaries, and (possibly) river mouths may also impact this species.
Geographical DistributionThe knifetooth sawfish occurs only in the Indo-Pacific. The western extent of its range is the Red Sea spanning east through the South China Sea to the Yellow Sea and southwestern Japan; and ranges south through the western Philippine Sea and Arafura Sea, to the Gulf of Carpentaria. In Australian waters it occurs from at least Cape Talbot (Timor Sea) east to the northern extent of the Great Barrier Reef (northern Coral Sea). It is moderately common in the Gulf of Carpentaria, Australia. The complete distribution of this species is still unclear.
The knifetooth sawfish is primarily a benthic species, and probably prefers sandy or muddy bottoms, but may occur over seagrass and other bottom types. This fish is known to occur most often in inshore areas, including estuaries, bays, and river mouths; from shallow water to at least 131 feet (40 meters). The knifetooth sawfish has been recorded far upstream in large rivers, including the Tachin River in Thailand, although these records may be the result of confusion with other sawfish species. Continued exploitation of deep-water fisheries may reveal this species to occur in deeper water than was previously known.
All sawfishes are highly modified and elongate rays having a shark-like body and a blade-like snout (termed 'rostrum') that has lateral, tooth-like denticles (termed 'rostral teeth') set into sockets. The presence of a rostrum having laterally protruding teeth separates sawfishes from all other batoids (skates and rays). These characteristics, along with the slender blade-like snout bearing 18-25 dorso-laterally flattened and broadened rostral teeth per side and the absence of rostral teeth at the base (closest to the head) easily distinguish knifetooth sawfish from other sawfish species.
In northern Australian waters, the rostral tooth count for knifetooth sawfish very between 18 and 22 per side. This species has a higher average rostral tooth count in other parts of the Indo-Pacific (24-25 per side). The rostral teeth may number more on one side of the rostrum than on the opposing side in this species.
The dorsal body surface of this species is grayish in color, fading to a pale gray color ventrally. Knifetooth sawfish rostral teeth are whitish in color, contrasting strongly with the gray rostrum. The base of the rostrum is sometimes a dark brown color. The fins are a pale gray, often lighter in color than that of the dorsal body surface.
Teeth of the knifetooth sawfish are similar in both jaws. This species exhibits many rows of blunt teeth with rounded cusps and smooth surfaces. The oral teeth of this species may show wear from use.
Dermal denticles along the body and fins of this species are very small and have a flat crown with three posterior cusps. A central cusp is surrounded by a lateral cusp on either side. The denticles along the rostrum and edges of fins are similar in shape and arrangement, although fin denticles are slightly larger. Denticles of adults are widely spaced except where concentrated along the anterior edges of the head and fins, while fetal specimens and young up to 25.3 in (64.2 cm) in total length are devoid of denticles. In a specimen measuring 28 inches (71 cm) long, denticles were present only on the anterior portion of the rostrum and along the anterior edge of all fins.
Size, Age & Growth
Nothing is known about the size, age, and growth of this species. In Australia this fish attains a maximum total length of about 11.5 ft (3.5 m). Unconfirmed reports of the knifetooth sawfish attaining much larger sizes elsewhere, such as19.7 ft (6.0 m) in India and 26.2 ft (8.0 m) in Thailand, seem doubtful. Young knifetooth sawfish probably measure 1.5-2.5 ft (0.5-0.8 M) in length at birth.
Despite the knifetooth sawfish' interesting mode of food gathering, using its rostrum in a side-to-side slashing motion to dislodge invertebrates from substrate and to stun schooling fishes, little is known about the feeding habits of this species. Known food items of this species include squids and small fishes. Other probable food items include crustaceans such as crabs and shrimps.
Knifetooth sawfish, like all sharks, skates, and rays, have internal fertilization. This species, like all rays, utilizes a strategy of embryo nourishment called aplacental yolk sac viviparity. With this strategy, the embryos are nourished only by their yolk sac, which provides energy for them to develop into fully functional young sawfish in utero. The embryos are nourished by yolk stored in a yolk sac, connected to the embryo by a yolk stalk and both of these structures are fully absorbed before the young sawfish are born. The gestation period of the knifetooth sawfish is not known, but the largetooth sawfish (Pristis perotteti) has a gestation period of about five months. Young knifetooth sawfish are probably born in the spring. Reported litter sizes range from 6 to 23 young, and each may measure between 1.5 and 2.5 feet (0.5-0.8 m) in total length, and are probably born tail-first. The saw teeth of young sawfish do not fully erupt, and are also covered in a sheath of tissue, until after birth so as not to injure the mother. Young knifetooth sawfish rostral teeth reach their full size proportionate to the size of the rostrum soon after birth. The reproductive cycle of the knifetooth sawfish is still not documented, but the largetooth sawfish has been reported to produce litters every other year.
This species falls prey to sharks, including hammerhead sharks (Sphyrna sp.). Other likely predators of the knifetooth sawfish include bull sharks (Carcharhinus leucas), copper sharks (Carcharhinus brachyurus), and saltwater crocodiles (Crocodylus porosus). When entangled in a net, this species becomes particularly vulnerable to predation.
The parasites Nonacotyle pristis and Neoheterocotyle darwinensis n. sp. inhabit the gills of other sawfishes off Darwin, Australia and in Papua New Guinea. These parasite species may also use the knifetooth sawfish as a host.
This species was first described as Pristis cuspidatus in 1794 by John Latham in his article entitled An essay on the various species of sawfish in the journal Transactions of the Linnaean Society of London. Latham described the species based on two rostra. Unfortunately, these rostra were not saved, although a single rostrum was illustrated in the article. It took nearly a century before a specimen was designated as a representative of the species, it is now cataloged at the Muséum National D'Histoire Naturelle in France. Three other synonyms exist for the knifetooth sawfish, Anoxypristis cuspidatus Latham 1794 (a misspelling and gender mismatch), Oxypristis cuspidatus (Latham, 1794), and Squalus semisagittatus Shaw 1804 (the last two being junior synonyms). In 1913, the author Hoffman renamed the genus for this species from Pristis to Oxypristis, noting differences in various morphological characters, including the rostral cartilage and neurocranial structures, and the positioning and shape of various fins. However, the genus name Oxypristis Hoffman, 1913 was preoccupied by the insect genus Oxypristis Signoret, 1861. To avoid homonym problems, workers by the names of White and Moy-Thomas simply added a prefix to create Anoxypristis in 1941. To date, the name for this species has changed only slightly, being currently valid as A noxypristis cuspidata (Latham, 1794). The generic name Anoxypristis means "sharp saw" in Greek and can be broken down to the terms oxy, meaning "sharp", and pristis, meaning "saw". The prefix an should probably not be referred to in a translation of the genus, as this later addition was added simply to avoid homonym problems. The specific name cuspidata is derived from the Latin word cuspidatus, meaning "pointed". Together, the scientific name Anoxypristis cuspidata refers to the sharp-sided, blade-like rostral teeth of the knifetooth sawfish.
Prepared by: Jason Seitz