Knifetooth sawfish (Anoxypristis cuspidata)

Also known as: Narrow sawfish, pointed sawfish
  
French: Poisson-scie
KingdomAnimalia
PhylumChordata
ClassChondrichthyes
OrderRajiformes
FamilyPristidae
GenusAnoxypristis (1)
SizeLength: up to at least 470 cm (2)

The knifetooth sawfish is classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix I of CITES (3).

The knifetooth sawfish is an unusual type of ray, with a shark-like body and a distinctive, elongated snout, or rostrum, known as a saw. In this species, the saw is particularly narrow and bears 16 to 29 pairs of flattened, dagger-shaped ‘teeth’, which are in fact highly modified and enlarged scales. The body is grey above, fading to paler grey below, with pale fins, and white teeth on the saw (2) (4) (5). Adults are much paler than juveniles, and may have a slight greenish tinge (2). The knifetooth sawfish can be distinguished from other sawfish species by the lack of teeth along the base of the saw, and by the distinct lower lobe of the caudal fin (2) (6) (7). Like all sawfish, it differs from the similar-looking sawsharks by having a more flattened body, gill slits beneath rather than on the sides of the head, and no fleshy ‘barbels’ on the sides of the saw (2) (5) (7). Although the knifetooth sawfish is reported to reach an impressive six metres or more in length, these records are unconfirmed (2) (4) (5) (6).

The knifetooth sawfish has a relatively wide distribution across the Indo-West Pacific, from the Red Sea and Arabian Gulf, east to Japan and South East Asia, and south to northern Australia (1) (2) (4) (5) (6).

The knifetooth sawfish is found mainly in inshore coastal waters, to depths of around 40 metres, where it is thought to spend most of its time on or near the bottom. It may also enter estuaries and river deltas, and has been reported to move upstream into rivers in some areas, although its occurrence in freshwater has yet to be verified (1) (2) (4) (5).

Relatively little is known about the diet of the knifetooth sawfish, although it is believed to feed on small fish and invertebrates, such as crabs, squid and shrimps, slashing the saw back and forth to stun or kill prey, or using it to dig for prey in the sand or mud. The saw can also be used in defence against predators such as sharks (2) (4) (5) (8) (9). As in all sawfish, the true teeth in the jaw are tiny, blunt and rounded in shape (2) (4) (9).

The knifetooth sawfish gives birth to between 6 and 23 live young, usually in spring, after a gestation period of several months (2) (4) (9). The young sawfish are quite large at birth, measuring around 40 to 80 centimetres in length (2) (4), and are born with a membranous sheath covering the saw, probably to prevent injury to the mother. The saw hardens and the membrane dissolves shortly after birth, after which the young are able to hunt small prey (4) (9) (10) (11). Little else is known about reproduction in this species, although it is thought to produce a litter only every other year (4) (11). Some sawfish species are believed to live for up to 30 years or more (9).

The knifetooth sawfish was once widespread and common throughout the Indo-West Pacific region, but its population has become increasingly small and fragmented, with the global population believed to have decreased by over 80 percent in the last 30 to 50 years (1) (6) (12). The unique structure of the saw makes all sawfish extremely vulnerable to entanglement and capture in a range of fishing gear, both in targeted fisheries and as accidental bycatch. Although most landings are accidental, the knifetooth sawfish is highly valued for its meat, fins, liver oil and skin, and when caught is usually retained. The saw is also highly valued, both as a curio and for use in traditional Chinese medicine (1) (2) (4) (6) (12). An increasing demand for live specimens for public aquaria may be putting further pressure on this species (1) (6) (11).

The knifetooth sawfish is also under threat from habitat loss and degradation due to a range of human activities, particularly in light of its distribution in coastal and estuarine waters, where pressures on aquatic environments are particularly great (1) (2) (4) (6) (10). The slow growth and reproductive rate of this species also mean that its populations are slow to recover once depleted (1) (6) (9) (12).

In 2007, the Convention on International Trade in Endangered Species (CITES) listed the knifetooth sawfish on Appendix I, meaning that international trade in the species is now banned (3). The knifetooth sawfish is legally protected in India (1) (6), but little other effective legislation appears to exist for the species elsewhere (4). In Australia, monitoring, research and recovery plans have been recommended for all sawfish (6) (11) (12), but the knifetooth sawfish has yet to be listed there under the Environment Protection and Biodiversity Conservation Act (EPBC) 1999 (1) (11). Recent advances in obtaining DNA samples from dry sawfish rostra (13), together with studies into DNA ‘barcoding’ from confiscated fins (14), may help fishing authorities to gather essential data on the illegal fishing of sawfish and other sharks and rays, hopefully assisting in the management and conservation of this unique and Endangered fish.

To find out more about the knifetooth sawfish and the conservation of sharks and rays, see:

 

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

  1. IUCN Red List (August, 2013)
    http://www.iucnredlist.org/
  2. Carpenter, K.E. and Niem, V.H. (1999) The Living Marine Resources of the Western Central Pacific. Volume 3: Batoid Fishes, Chimaeras and Bony Fishes. Part 1 (Elopidae to Linophrynidae). Food and Agriculture Organisation of the United Nations, Rome. Available at:
    ftp://ftp.fao.org/docrep/fao/009/x2401e/x2401e00.pdf
  3. CITES (October, 2009)
    http://www.cites.org
  4. Knifetooth Sawfish Biological Profile, Ichthyology Department, Florida Museum of Natural History (October, 2009)
    http://www.flmnh.ufl.edu/fish/Gallery/Descript/KTSawfish/KTSawfish.html
  5. Randall, J.E. (1995) Coastal Fishes of Oman. University of Hawaii Press, Honolulu, Hawaii.
  6. Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (2005) Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. Status Survey. IUCN/SSC Shark Specialist Group, IUCN, Gland. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/2005-029.pdf
  7. Daley, R.K., Stevens, J.D., Last, P.R. and Yearsley, G.K. (2002) Field Guide to Australian Sharks and Rays. CSIRO Publishing, Collingwood, Australia.
  8. Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.
  9. Department of Fisheries, Government of Western Australia: Fact Sheet 7 - A Saw Subject (October, 2009)
    http://www.fish.wa.gov.au/docs/pub/FactSheets/Fisheries%20Fact%20Sheet%207%20-%20Sawfish.pdf
  10. ReefQuest Centre for Shark Research (October, 2009)
    http://www.elasmo-research.org/education/shark_profiles/pristiformes.htm
  11. Australian Government: Department of the Environment, Water, Heritage and the Arts - Sawfish (October, 2009)
    http://www.environment.gov.au/coasts/species/sharks/sawfish/index.html
  12. Pogonoski, J.J., Pollard, D.A. and Paxton, J.R. (2002) Conservation Overview and Action Plan for Australian Threatened and Potentially Threatened Marine and Estuarine Fishes. Environment Australia, Canberra, Australia. Available at:
    http://www.environment.gov.au/coasts/publications/marine-fish-action/pubs/marine-fish.pdf
  13. Phillips, N., Chaplin, J., Morgan, D. and Peverell, S. (2009) Extraction and amplification of DNA from the dried rostra of sawfishes (Pristidae) for applications in conservation genetics. Pacific Conservation Biology, 15(2): 128 - 134.
  14. Holmes, B.H., Steinke, D. and Ward, R.D. (2009) Identification of shark and ray fins using DNA barcoding. Fisheries Reseearch, 95: 280 - 288.