Fishes · Rays · Sawfish

Longcomb sawfish

Pristis zijsron Bleeker, 1851

syn. Pristis zisron, Pristis zyrson, Pristis zysron, Pristis zysross

6 - 7.3 m1-70 mCITES ICritically Endangered

870

The longcomb or green sawfish (Pristis zijsron) is a sizable species characterized by a robust, heavily-set body and a distinctive rostrum, adorned with 23-37 paired rostral teeth that are more closely spaced at the tip than at the base. The rostrum measures approximately 23-33% of the total body length. The first dorsal fin's origin is notably posterior to that of the pelvic fins, and the dorsal posterior margins are either straight or slightly concave. The pectoral fins are elongated and narrow, with anterior margins that are mildly convex and posterior margins that are straight. The caudal fin exhibits a weakly convex posterior margin in juveniles, which becomes straight in adults, and lacks a distinct lower caudal lobe and secondary lateral keel beneath the primary caudal keel at its base.

The dorsum of the green sawfish is typically greenish-brown or olive, while its ventrum and rostral teeth are white. This species predominantly inhabits coastal marine, mangrove, and estuarine environments, extending to depths exceeding 70 meters and exhibiting some presence far offshore. It can reach a maximum length of 7.3 meters, with newborns measuring approximately 80 centimeters.

Historically, the green sawfish was widespread across the 🌊 Indian Ocean and southwestern Pacific. However, it is now seldom encountered and potentially extinct in many areas of its former range. Remaining populations are found in the Gulf of Arabia, the 🌊 Red Sea, and throughout Southeast Asia and northern 🇦🇺 Australia.

The species reproduces via aplacental lecithotrophic viviparity, with litters averaging around 12 individuals. Its diet likely comprises crustaceans and other benthic invertebrates, while its largely sedentary nature has been observed through tagging studies in Northern 🇦🇺 Australia's Gulf of Carpentaria, where individuals traverse less than 200 meters in a 24-hour period.

Encounters with the green sawfish by divers or snorkelers are exceedingly rare, with the species generally elusive and difficult to approach, particularly due to poor visibility and the presence of saltwater crocodiles in Northern 🇦🇺 Australia.

Conservation Status: Critically Endangered

The green sawfish is listed as Critically Endangered due to its low rates of population increase and significant susceptibility to fishing pressures, particularly from gillnets and demersal trawl nets. The species has experienced drastic population declines across its range, exacerbated by historical commercial fishing activities. Though some protective measures have been implemented, such as no-take zones in several range states (including 🇦🇺 Australia, Bahrain, and 🇮🇳 India) and inclusion in CITES Appendix I, these efforts are insufficient to guarantee its survival globally. The population is suspected to have declined by over 80% in the past three generations (~44 years), with possible localized extinctions in certain regions. Despite a lack of precise quantitative data, available evidence suggests the species is now considerably rarer throughout its range, with 🇦🇺 Australia hosting some of the last viable populations.

Why it's threatened

Residential & commercial development

Housing & urban areas · Commercial & industrial areas

Energy production & mining

Oil & gas drilling · Mining & quarrying

Biological resource use

Intentional use: (subsistence/small scale) [harvest] · Intentional use: (large scale) [harvest] · Unintentional effects: (subsistence/small scale) [harvest] · Unintentional effects: (large scale) [harvest]

Natural system modifications

Large dams · Abstraction of surface water (agricultural use)

Climate change & severe weather

Habitat shifting & alteration · Temperature extremes

The Green Sawfish is subject to intense fishing pressure that is poorly managed or unregulated across much of its range. The species is taken as bycatch in commercial and small-scale fisheries (inclusive of artisanal, cultural, and subsistence) with a variety of fishing gears including gillnet, trawl, and line. The toothed rostra of sawfish make them highly susceptible to entanglement particularly in gillnets and trawls. Fishing effort has increased over the past decades across most of the species’ range with the fin and meat trade driving increasing demand and exploitation of many elasmobranchs (Chen 1996, Jabado et al. 2017, Okes and Sant 2019, Yan et al. 2021). In most instances throughout the range of this species, it is retained for at least its fins, rostra, and meat (CITES 2007, Yan et al. 2021). Within Australia and other jurisdictions where fishers are required to release sawfishes, at-vessel- and post-capture-mortality of captured sawfishes may still be high as individuals may be euthanized or have their rostrum removed in order to safely or efficiently untangle them from fishing gear (Morgan et al. 2016).

The inshore freshwater, estuarine, mangrove, and coastal habitats used by the species are threatened by habitat loss and degradation (CITES 2007). For example, in Southeast Asia, mangrove areas have been reduced by an estimated 30% since 1980 (Polidoro et al. 2010). For Green Sawfish, habitat loss or degradation is most concentrated on essential nearshore and estuarine nursery habitats. There may also be impacts on adult Green Sawfish associated with offshore oil and gas extraction (e.g., seismic surveys) which occurs in several areas within their range (e.g., the Australian Northwest Shelf, northwest Indian Ocean).

Historically, the northwest region of Australia has been relatively undeveloped and sparsely populated, and as a result has large areas of undisturbed coastal habitats. At present, there are several additional factors that may pose major threats to Green Sawfish in Western Australia (WA). These include a range of coastal developments, including various mining and natural resource operations which have export facilities along the WA coastline (Devillers et al. 2015). These include oil and gas and mining operations that have export facilities along the coastline, as well as substantial salt mining operations with seawater intakes and outtakes and export facilities. These operations include coastal developments such as lighted jetties, dredged shipping channels, and offloading structures with sea walls. For juvenile Green Sawfish using this area, tracking data suggests that such structures may hinder small juveniles from moving along the coastline (K. Lear and D. Morgan unpubl. data 2022), and therefore the increased numbers of these structures appearing in WA could cause some population fragmentation or destruction of important juvenile habitats for this species.

Threat classification from the IUCN Red List.