|Scientific Name:||Pristis pristis (Indo-West Pacific subpopulation)|
See Pristis pristis
Pristis microdon Latham, 1794 (Indo-West Pacific)
|Taxonomic Notes:||In a recent study, Faria et al. (2013) demonstrated that the existing taxonomy of the Pristidae required modification, recognising a total of five species in two genera. Pristis pristis had been recognised previously as consisting of up to three species (Pristis pristis, P. microdon and P. perotteti), but utilising a combination of mitochondrial DNA and morphological characters appears to be one species. While the P. pristis group is best considered a single species, it can be composed of a network of geographical units (subpopulations) that are not genetically distinct, but may be considered ecologically different.
Largetooth Sawfish (Pristis pristis) was previously referred to as Freshwater Sawfish (P. microdon) in the Indo-West Pacific.
|Red List Category & Criteria:||Critically Endangered A2cd ver 3.1|
|Assessor/s:||Kyne, P.M., Carlson, J. & Smith, K.|
|Reviewer/s:||Pillans, R. & Harrison, L.|
Indo-West Pacific Largetooth Sawfish (Pristis pristis) were once widespread from parts of the Western Indian Ocean, through India, the Bay of Bengal and Southeast Asia to New Guinea and northern Australia. Large-scale population declines and extirpations have occurred across the species’ former range, and while there is uncertainty regarding its status in parts of the region, Australia now likely comprises a high proportion of the regional subpopulation (indeed, the global population of the species). Recent records from elsewhere in the Indo-West Pacific are now extremely rare; in places the species was once described as ‘common’ or ‘abundant’. All sawfishes have also undergone significant, albeit largely unquantified, declines in Australia, and although protection and management is in place in Australia, there is no evidence to suggest population recovery. Regionally, a population reduction of ≥80% is inferred based on a reduction in extent of occurrence (EOO) over a period of three generations (i.e., 1969 to present). The subpopulation is considered to be Critically Endangered given declines and continuing threats; much of the species’ former Indo-West Pacific range, with the exception of northern Australia, is subject to intense human pressure, particularly through generally unregulated and unmanaged fisheries, and habitat loss and degradation in critical sawfish habitats.
|Range Description:||The Indo-West Pacific subpopulation of the Largetooth Sawfish was formerly wide-ranging from parts of the Western Indian Ocean through India, the Bay of Bengal and Southeast Asia to New Guinea and northern Australia. Its current distribution is now patchy across its range. It had been confirmed from several major river systems of Papua New Guinea, Indonesia and Malaysia (including Borneo), Cambodia, Viet Nam and the Philippines (Roberts 1978, Tan and Lim 1998, Compagno et al. 2005, Stevens et al. 2005). Its occurrence in many of these is now uncertain or non-existent. It may now be extinct in several range states, including South Africa, the Seychelles, Thailand and others; elsewhere it has been severely depleted.
Northern Australia may be the last viable population stronghold in the Indo-West Pacific, although it may persist in remote parts of the region. It occurs across tropical northern Australia from the northeastern coast of Queensland, across Cape York, the Gulf of Carpentaria, the Northern Territory and the Kimberley region (Western Australia). It has occurred as a vagrant to southwestern Australia (Last and Stevens 2009).
Native:Australia (Northern Territory, Queensland, Western Australia); Bangladesh; India; Madagascar; Mozambique; Pakistan; Papua New Guinea; Somalia
Possibly extinct:Cambodia; Lao People's Democratic Republic; Malaysia; Seychelles; Singapore; South Africa; Thailand
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Indian Ocean – western; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
There are almost no data on population status of Largetooth Sawfish across the Indo-West Pacific; all populations are, however, probably severely depleted.
Landings of Largetooth Sawfish are now extremely rare in former range states of the Western and Northern Indian Ocean. Although the St Lucia estuary system of South Africa was once an important breeding area, sawfishes (including Largetooth Sawfish) now appear to be extinct in that country. They also now appear to be absent from southern Mozambique (S. Pierce pers. comm. 2012) and while once common in the Zambezi River (Wallace 1967) no recent sightings have been documented. Madagascar, the Seychelles, Pakistan and India, amongst other Indian Ocean range states, have all seen depletions of sawfishes, including Largetooth Sawfish. Sawfish were previously common in artisanal fishing catches on the western coast of Madagascar, but are now extremely rare along that coast (Manach et al. 2011). There are no sawfish records from the Seychelles in the last decade (D. Rowat pers. comm. 2012), and a 2009 record of a Largetooth Sawfish in Gwadar, western Balochistan, Pakistan (A. Rahim pers. comm. 2012) represents a very rare event. Surveys with fishers in Raigad District (Maharashtra state) of India (where sawfishes were commonly harvested historically) indicate a drastic decline in the sawfish fishery from 1985–1990, with only occasional catches in recent years (R. Raut pers. comm. 2012).
In Southeast Asia, localised depletions and extinctions of sawfishes have been reported or inferred from across the region. During some eleven years of market surveys (over 160 visits to 11 market sites) in various parts of Indonesia only two individual sawfish (both Largetooth Sawfish) were recorded which were caught in the Arafura/Banda Sea region (W. White pers. comm. 2012) and possibly came from illegal fishing in Australian waters. Demersal elasmobranchs are intensively targeted in Indonesia (Blaber et al. 2009), and this extremely low occurrence (out of some 60,000 chondrichthyans examined) is indicative of severely depleted populations in Indonesia. In fact, it is thought that sawfishes are extinct from large areas of Indonesia. Despite the presence of sawfish rostra in houses near fishing ports, local Indonesian fishermen indicate that they have not seen sawfishes for more than 20 or 30 years (W. White pers. comm. 2012). Populations in Borneo are thought to be seriously depleted (Last et al. 2010). In Sabah (Malaysian Borneo), fishers and villagers reported sawfish as abundant in the 1970s and declining sharply in the 1980s, with very limited catches since that time (Manjaji 2002). The last known record from the Kinabatangan River was in 1996 (B.M. Manjaji-Matsumoto pers. comm. 2012).
Datasets from as early as 1963–1972 showed the considerable decline in batoids in the Gulf of Thailand (Pauly 1979), which included the virtual disappearance of sawfish (Pauly 1988). Declines in demersal fishes in the Thai Andaman Sea were also documented (Pauly 1979) and these likely included sawfishes. In contrast, historic accounts indicated that sawfishes were ‘common’ and caught in ‘considerable numbers’ in Thailand, including in rivers (Smith 1945). Within the Cambodian Mekong system, numbers of Largetooth Sawfish have reportedly decreased considerably. Historically, they were regularly seen as far upstream as Khoné Falls, and in other areas of the Mekong (Tonlé Sap and Great Lake), none have been seen for ‘several decades’ (Rainboth 1996).
Largetooth Sawfish were considered common in the Philippines by Herre (1953) but none were recorded in more recent surveys and it is thought that the population ‘has greatly declined in the Philippines’ (Compagno et al. 2005).
Largetooth Sawfish had previously been described as common in the middle reaches and large tributaries of the Fly River, Papua New Guinea (Roberts 1978) but its status there requires reappraisal. More recently, the ‘demise’ of the species has been reported in Lake Sentani, West Papua as a result of the change from traditional fishing methods to the use of gill nets (Polhemus et al. 2004).
All sawfish species have undergone significant, albeit largely unquantified, declines in Australia. In places, viable populations persist, representing some of the last viable populations in the Indo-West Pacific, with Australia being one of a limited number of global strongholds for sawfishes (Stevens et al. 2005, DSEWPaC 2011a). Genetic data indicate that Largetooth Sawfish has moderate levels of genetic diversity and male-biased dispersal in Australian waters (Phillips et al. 2011, Phillips 2012). Genetic evidence suggests that females have strong reproductive philopatry (returning to sites previously used for reproduction), with maternal population structuring between Western Australia and the Gulf of Carpentaria, with the northern coast of the Northern Territory and the Queensland east coast populations also potentially forming distinct maternal populations (Phillips et al. 2011). In contrast, males disperse between at least Western Australia, the Northern Territory and the Gulf of Carpentaria (Phillips 2012).
Species-specific data to accurately ascertain the status of Australian sawfishes is generally lacking and the evidence for decline and range contraction is largely anecdotal. Data from the Queensland Shark Control Program, which operates ‘bather protection’ fishing gear along the Queensland east coast, shows a clear decline in sawfish catch (non species-specific) over a 30 year period from the 1960s and the complete disappearance of sawfish in southern Queensland (Stevens et al. 2005). All Pristis species are now extremely rare along the Australian east coast (the area in which human population and habitat modification is greatest) where they have undergone a considerable range contraction. Although populations across northern Australia have undergone significant reduction and their status is uncertain, Australian populations are considered some of the highest in the world.
While specific management measures are now in place in Australia, including full species protection, education of fishers about safe release practices, and fishery-specific management, threats are ongoing and there is no information to suggest that the population is recovering from previous declines.
Across the Indo-West Pacific, a population reduction of ≥80% is inferred based on a reduction in extent of occurrence (EOO) over a period of three generations (i.e., 1969 to present). Declines and continuing threats (much of the species’ Indo-West Pacific range, with the exception of northern Australia, is subject to intense human pressure, particularly through generally unregulated and unmanaged fisheries, and habitat loss and degradation in critical sawfish habitats) are resulting in the continual declines of remnant populations. The Australian population of Largetooth Sawfish likely comprises a high proportion of the global population (Stevens et al. 2005).
|Habitat and Ecology:||
Available life history information on Largetooth Sawfish comes from in Lake Nicaragua in Central America (Thorson 1976; 1982) and from northern Australia.
Largetooth Sawfish are generally restricted to shallow (<10 m) coastal, estuarine, and fresh waters, although they have been found at depths of up to 26 m in Lake Nicaragua. Largetooth Sawfish move across salinity gradients freely and in northern Australia, parturition probably occurs in brackish or saltwater and juveniles spend ~4–5 years in the freshwater reaches of rivers and floodplain waterholes before migrating to estuarine and marine waters (Thorburn et al. 2007, Peverell 2008, Whitty et al. 2008, Whitty et al. 2009, P. Kyne unpublished data).
The life history of Largetooth Sawfish, like many elasmobranchs, is characterised by slow growth, late maturity, and low fecundity, which generally contributes to a low intrinsic rate of increase. The maximum reported size of Largetooth Sawfish is 656 cm TL, although it has been estimated up to 700 cm TL (Compagno and Last 1999). Very large individuals are now rarely seen anywhere in the Indo-West Pacific.
The reproductive method of sawfishes is most likely lecithotrophic viviparity. The only known reproductive study of Largetooth Sawfish was from Lake Nicaragua in the 1970s (Thorson 1976) with other observations from northern Australia. Thorson (1976) found that both ovaries appeared to be functional, though the left seemed to be larger and carry more ova. Litter sizes in Lake Nicaragua were 1–13 (mean 7.3) following a gestation period of about five months. While the reproductive cycle is possibly biennial in the Western Atlantic (Thorson 1976), it appears to be annual in northern Australia (Peverell 2008).
Size at birth ranges 72–90 cm TL (Peverell 2008). Size at maturity is ~300 cm TL for females and ~280–300 cm TL for males (Thorburn et al. 2007, Peverell 2008, Whitty et al. 2008). Age at maturity in Queensland, northern Australia, has been estimated at 8–10 years (Peverell 2008). Peverell (2008) using a preliminary vertebral growth ring analysis estimated a maximum age of 35 years in northern Australia.
Using life history information from populations in Central America, Simpfendorfer (2000) estimated an intrinsic rate of increase of 0.05 to 0.07 per year and population doubling times of 10.3–13.6 years. These rates were estimated under ideal conditions (i.e. no fisheries, no population fragmentation, no habitat modification and no inbreeding depression). Moreno Iturria (2012) estimated an intrinsic rate of population increase of 0.12 yr-1, a population doubling time of 5.8 yrs and a generation time of 14.6 yrs for Indo-West Pacific Largetooth Sawfish.
The principal threats to this species are from fishing; it was formerly targeted, but is now mostly taken incidentally in broad-spectrum fisheries (CITES 2007). The long toothed rostrums of sawfishes make them extraordinarily vulnerable to entanglement in any sort of net gear, gillnetting and trawling in particular. The exploitation of elasmobranchs is high in many parts of the Largetooth Sawfish’s range in the Indo-West Pacific, particularly in coastal areas and freshwater systems. Unregulated and unmanaged fisheries, and habitat loss and degradation all threaten sawfishes across the region. Considerable population declines and localised extinctions have been reported for sawfish species in the region.
For at least part of its life cycle, the Largetooth Sawfish relies on a variety of specific habitat types including freshwater systems, estuaries and mangroves; these are all affected by human development (CITES 2007). Agricultural and urban development, commercial activities, dredge-and-fill operations, boating, erosion, and diversions of freshwater runoff as a result of continued coastal and catchment development has caused substantial loss or modification of these habitats (CITES 2007). Mining activities, in northern Australia, New Guinea (e.g., the Fly River) and elsewhere, pose a risk to Largetooth Sawfish through freshwater habitat alteration or potential pollution events. Alterations to river courses are a realised threat to Largetooth Sawfish which migrate upstream in early life stages. These range from smaller barrages and road crossing in northern Australia to large-scale river alterations in Southeast Asia.
In Australia, datasets indicate that net fisheries account for the greatest bycatch of sawfish (all species) across northern Australia (80.2%) followed by trawling (16.6%), line fishing (9.2%) and recreational fishing (0.3%) (Stevens et al. 2005). Largetooth Sawfish are captured by all these fishing activities (Giles et al. 2004) and declines in Largetooth Sawfish are suspected based on potential levels of exploitation (Larson et al. 2006). A survey across northern Australia from Western Australia to Queensland appears to support the assertion that fishing is responsible for declines, as it found greater numbers of sawfish in areas of lower fishing pressure (both commercial and recreational) (Thorburn et al. 2003). The sustainability of Largetooth Sawfish populations in northern Australia is considered to be at high risk due to the cumulative effects of all fisheries, and the species’ low biological productivity and susceptibility to gillnets (Salini et al. 2007).
A number of Queensland, Northern Territory and Western Australian inshore net fisheries continue to catch Largetooth Sawfish incidentally. Despite requirements to release these, there is no doubt a continuing level of bycatch-associated mortality.
The extent to which recreational fishers interact with Largetooth Sawfish across northern Australia is unknown, but in some areas where the species has been recorded, recreational fishing is a popular activity, which is increasing in popularity and could pose a threat to the species. In the Fitzroy River (WA), recreational fishers have been reported killing incidentally caught Largetooth Sawfish for the ‘trophy’ rostrum and for retrieval of fishing tackle (Thorburn et al. 2003).
Sawfish (non species-specific records) have been recorded in derelict fishing nets in northern Australian waters; the Gulf of Carpentaria is a particular hotspot for these ‘ghost nets’ (Gunn et al. 2010) and capture in these may result in sawfish mortality. Because of their toothed rostrum, sawfish may be exceptionally susceptible to entanglement in other types of marine debris, and entanglement has been reported in a number of types of marine debris (Seitz and Poulakis 2006). Entanglement in discarded or lost recreational fishing line may occur on occasion, as has been documented for Largetooth Sawfish in Western Australia (Thorburn et al. 2004).
All species of sawfish are listed on Appendix I of the Convention on International Trade of Endangered Species (CITES), which effectively bans commercial international trade in sawfish or their parts.
Within Australia, Largetooth Sawfish has the following conservation and protected status listings: Australian Commonwealth waters, Vulnerable (Environment Protection and Biodiversity Act 1999); Queensland, Protected (Fisheries Act 1994); Northern Territory (NT), Vulnerable (Territory Parks and Wildlife Conservation Act 2000); Western Australia (WA), Totally Protected (Fish Resources Management Act 1994). The take of the species is therefore prohibited within Australian Commonwealth, state and territory waters.
In addition to the above legislated regulations, the Commonwealth, Queensland, NT and WA all have fisheries management plans in place for interactions with protected species, including Largetooth Sawfish. These include mandatory reporting of interactions with these species, release of live animals, observer coverage of most of the fisheries (although this is very low in state and territory fisheries which are likely to interact with Largetooth Sawfish) and education programmes for fishers on identification and ways to minimise interactions with this species. The Queensland Government has published a guide to the safe release of sawfish for commercial fishers (DEEDI 2010) and NT shark fishers have a Code of Practice for the release of live sawfish from gillnets (Salini et al. 2007).
Several spatial closures in riverine, estuarine and coastal waters in the NT Barramundi Fishery offer Largetooth Sawfish some refuge from commercial gillnet fishing activities in the NT. Closed areas within the Great Barrier Reef Marine Park and the closure of rivers in Princess Charlotte Bay to gillnetting may also afford some protection. Seasonal spawning closures for the take of Barramundi (Lates calcarifer) (mostly during the summer wet season) throughout much of the range add a level of protection to the species, however, information on Largetooth Sawfish long-term movement patterns and habitat use are required in order to assess the benefits of closed areas and seasons not specifically designed for sawfish.
In northern Australian prawn trawl fisheries, the use of turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs) is mandatory, though the benefit of these devices on sawfish is poorly quantified. In one study, they have been shown to reduce the catch of Narrow Sawfish (Anoxypristis cuspidata), however, they and other sawfish species are still being caught as their rostra become tangled in the body of the net (Brewer et al. 2006).
Outside of Australia, awareness needs to be raised, and regulations put in place to protect all sawfishes and promote population recovery. While sawfishes (including Largetooth) are theoretically protected in India (Indian Wildlife (Protection) Act), threats continue with little beneficial management, although increasing awareness of sawfishes in India is encouraging. Largetooth Sawfish are also protected in Bangladesh, Malaysia and Indonesia. Although protected in these range states, the lack of enforcement or specific fisheries regulations, and ongoing gillnet and trawl fisheries, means that the threats are ongoing.
|Citation:||Kyne, P.M., Carlson, J. & Smith, K. 2013. Pristis pristis (Indo-West Pacific subpopulation). In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 12 December 2013.|
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