Spatial distribution and habitat utilisation of sawfish (Pristis spp) in relation to fishing in northern Australia
By J.D Stevens, CSIRO Marine and Atmospheric Research, Hobart;
R.B. McAuley Department of Fisheries, Government of Western Australia, Perth;
C.A. Simpfendorfer James Cook University, Townsville;
R.D. Pillans CSIRO Marine and Atmospheric Research, Cleveland.
A report to Department of the Environment, Water, Heritage and the Arts, September 2008
About the document
Up to seven species of sawfish (Family Pristidae) belonging to two genera (Anoxpristis and Pristis) occur around the world. Both genera, and four species, occur in Australia (Last and Stevens 1994). Further taxonomic research is required to resolve nomenclatural issues and provide definitive identifications of some species. The narrow sawfish (Anoxypristis cuspidata), dwarf sawfish (Pristis clavata), freshwater sawfish (Pristis microdon) and green sawfish (Pristis zijsron) occur mainly in inshore coastal waters and riverine environments of tropical northern Australia.
Because of their rostra, sawfish are particularly vulnerable to capture in all forms of net fishing gear. Their large size (up to 7 m) and power can pose a real threat to fishers, which means that live release has been rarely practised in the past. Sawfish fins are particularly valuable in the international fin trade and the flesh is also of good quality so there is usually a major incentive for targeting them or retaining them when taken as bycatch. Together with their generally low biological productivity (Peverell 2005), environmental degradation of their habitats has meant that most populations of sawfish around the world have either been extirpated over much of their original distribution or at least suffered major declines in abundance as well as reductions in their range (Cook et al. 2006). Australia, in particular areas of the Kimberley and Pilbara regions of north western Australia, probably represent some of the last relatively healthy populations of sawfish in the world. However, even in this region sawfish numbers might have been reduced by commercial and recreational fishing. Stobutzki et al. (2000) assessed sawfish as the species at greatest risk of unsustainable fishing in northern Australia. Recognising this, two species (P. microdon and P. zijsron) are listed as Vulnerable on the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and most sawfish species are given some level of protection in all northern States and the Territory (Pogonoski et al. 2002). All sawfish are listed as Totally Protected under the Western Australian Fish Resources Management Act (FRMA).
They are all listed as critically endangered on the IUCN (World Conservation Union) Red List and are also listed on Appendix 1 of CITES, with the exception of P. microdon that is listed on Appendix 11. These instruments provide some protection from international trade. The biology and ecology of sawfish in Australia have received little attention until recently when increased funding opportunities resulting from their elevated conservation status focused attention on them (Thorburn et al. 2003, 2007).