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Green Sawfish (Pristis zijsron)

The green sawfish is the largest sawfish, a ray of shallow coastal waters and estuaries across northern Australia that also uses deeper offshore water as an adult. It is Vulnerable and listed migratory under the EPBC Act, and Vulnerable in Western Australia and the Northern Territory. The Ashburton River delta near Onslow in the Pilbara is the best known nursery in Australia.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

Northern Territory, Territory Parks and Wildlife Conservation Act 1976: Vulnerable.

Western Australia, Biodiversity Conservation Act 2016: Vulnerable.

Commonwealth, EPBC Act 1999: Listed migratory. Listed under the Bonn Convention. Listed migratory species are a matter of national environmental significance, so a significant impact needs referral.

Seasonal planning

Pupping period of about August to December estimated for the Pilbara. Use as a planning window for dredging and construction near nursery creeks.

Breeding mode: Live young.

Timing varies between rivers and years.

  • Pupping and newborns in Pilbara nurseries: Pupping period of about August to December estimated for the Pilbara. Use as a planning window for dredging and construction near nursery creeks.

Identification: Appearance and size

Morgan et al. (2017) describe it as the largest of the sawfishes. DCCEEW gives a size of at least 5 m.

Morgan et al. (2017) describe it as the largest of the sawfishes. DCCEEW gives a size of at least 5 m.

Identification: Similar species

It overlaps with the dwarf, freshwater and narrow sawfish. Separating sawfish species needs care with saw shape and tooth counts. Photograph the saw and fins if one is seen and release it without delay.

Distribution: Australian range

Occurs mostly in tropical waters across northern Australia. DCCEEW notes records as far south as Sydney and Broome, and the FRDC report notes its Australian range has contracted.

Occurs mostly in tropical waters across northern Australia. DCCEEW notes records as far south as Sydney and Broome, and the FRDC report notes its Australian range has contracted.

Distribution: Western Australia

In WA the southern Pilbara, around the Ashburton River delta, Hooley Creek and nearby mangrove creeks, holds a recognised nursery used every year.

Habitat: Estuary and coastal habitat

Shallow coastal and estuarine waters with mud or sand flats and mangroves. Morgan et al. (2017) found juveniles used nearshore coastal habitat at low tide and protected mangrove creeks at high tide, staying close to the Ashburton River mouth (within 700 m upstream).

Shallow coastal and estuarine waters with mud or sand flats and mangroves. Morgan et al. (2017) found juveniles used nearshore coastal habitat at low tide and protected mangrove creeks at high tide, staying close to the Ashburton River mouth (within 700 m upstream).

The FRDC report notes adults occur more broadly, on the continental shelf to depths of 70 m or more.

Habitat: Site inspection points

Map mangrove creeks, tidal flats, river mouths and deeper estuary pools within and downstream of the works, and note any structures that cross or narrow tidal channels.

Foraging habitat: Diet

Sawfish mainly feed on crabs, shrimps and other bottom-dwelling invertebrates, crushing their food and swallowing it whole.

Sawfish mainly feed on crabs, shrimps and other bottom-dwelling invertebrates, crushing their food and swallowing it whole.

Breeding habitat: Breeding and nurseries

Pupping in the Pilbara is estimated at about August to December. Kinship work in the Ashburton River estuary found evidence that females return to the same pupping sites. Neonates stay in their primary nursery for about a year before spreading into nearby creeks.

Pupping in the Pilbara is estimated at about August to December. Kinship work in the Ashburton River estuary found evidence that females return to the same pupping sites. Neonates stay in their primary nursery for about a year before spreading into nearby creeks.

DCCEEW notes sawfish are thought to breed every other year, with an average of about eight live pups.

Sheltering habitat: Shelter

Protected tidal mangrove creeks at high tide. Morgan et al. (2017) found juveniles left the Ashburton estuary when cyclonic rain brought high freshwater flows and turbidity.

Protected tidal mangrove creeks at high tide. Morgan et al. (2017) found juveniles left the Ashburton estuary when cyclonic rain brought high freshwater flows and turbidity.

Threats: Threats

The FRDC report names fishing as the primary global threat, with habitat loss from coastal development, pollution, loss of genetic diversity and climate change also listed.

The FRDC report names fishing as the primary global threat, with habitat loss from coastal development, pollution, loss of genetic diversity and climate change also listed.

A James Cook University study found a piled jetty and rock wall near the Ashburton nursery constrained juvenile movement between creek systems, although pupping continued.

Threats: Works risk

Dredging, reclamation, causeways, rock walls, jetties, culverts and water intakes in estuaries and tidal creeks, as well as turbidity, changes to tidal flow and night lighting over nursery creeks.

Survey methodology: 1. Desktop assessment

Sawfish surveys need permits, trained handlers and methods designed to avoid harm.

Check SNES, Atlas of Living Australia and DBCA records, Traditional Owner and ranger knowledge, and published nursery studies for the estuary.

Survey methodology: 2. Field detection

Specialist programs use short-set, closely watched nets and acoustic tagging under animal ethics approval, following protocols such as the Charles Darwin University sawfish procedures. Do not set unattended nets.

Survey methodology: 3. Limits

Sawfish are mobile and patchily detected, and a non-detection does not show absence. Use seasonal timing from this profile and expert advice.

Vegetation associations: Mangrove

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

Shallow coastal and estuarine waters with mud or sand flats and mangroves.

Automatically indexed from existing profile text. Not a verified preference, mapped occurrence or habitat requirement. Check the original source and regional qualifiers before use.

Evidence: Unreviewed profile-derived candidate

Confidence: Not independently verified

Region: Scope as described in the quoted profile text; not independently verified. Profile states: WA, NT, QLD.

Habitat use: general

Ecosystem associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific ecosystem association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Soil and substrate associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific soil association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Water and wetland associations: Water-associated habitat mentioned in profile

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

Morgan et al. (2017) found juveniles used nearshore coastal habitat at low tide and protected mangrove creeks at high tide, staying close to the Ashburton River mouth (within 700 m upstream).

Automatically indexed from existing profile text. Not a verified preference, mapped occurrence or habitat requirement. Check the original source and regional qualifiers before use.

Evidence: Unreviewed profile-derived candidate

Confidence: Not independently verified

Region: Scope as described in the quoted profile text; not independently verified. Profile states: WA, NT, QLD.

Habitat use: general

Fauna records and mapped habitat: Not yet analysed

Record locations can be overlaid with mapping, but record frequency alone does not measure habitat preference. No species is excluded from desktop assessments by this analysis.

No quality-controlled record-to-map analysis has been completed for this species. The existing generalised distribution dots and indicative range polygons have not been treated as precise occurrence coordinates.

A defensible run needs dated, independently attributable records, coordinate uncertainty, duplicate and captive-record checks, layer versions and regional scope. Preference and absence require additional survey-effort and detection evidence.

Habitat limitations and contrary evidence: No supported exclusion recorded

Not recorded is not the same as cannot occur. Low suitability, resident habitat, breeding habitat and occasional movement are different conclusions.

This library has not established a vegetation, ecosystem or soil-type exclusion for this species. This does not mean all habitat is suitable; the evidence needed to justify an exclusion has not been assembled.

Habitat limitations and contrary evidence: Before using a negative association

  • Confirm the taxon, geographic region, life stage and habitat function covered by the evidence.
  • Check survey methods, season, repeated effort and detectability before interpreting non-detection.
  • Investigate credible contradictory records and microhabitats absent from broad mapping.
  • Do not convert a missing map class, low record count or failed data request into species absence.

Before habitat disturbance: 1. Approvals

Confirm approvals and plan in-water works to avoid nursery habitat and key seasons.

The species is EPBC listed threatened and migratory, so actions likely to have a significant impact need referral. In WA, taking or disturbing listed fauna needs authorisation under the Biodiversity Conservation Act 2016.

Before habitat disturbance: 2. Timing and design

Schedule dredging, piling and causeway works outside the nursery period where possible, keep tidal channels open, and design crossings to maintain passage.

During habitat disturbance: 1. Controls

Keep in-water works controlled and watched.

Use turbidity controls, soft-start piling, screened intakes and spotters during in-water works. Stop works if a sawfish is seen in the work zone until it leaves.

During habitat disturbance: 2. Entanglement

If a sawfish is entangled, keep it in the water, cut the net away from the saw and release it. Never remove or damage the saw. Report the encounter to DBCA or the NT or Queensland agency.

After habitat disturbance: 1. Records

Record outcomes and report encounters.

Record any sightings, captures, injuries and deaths with location, size and photographs, and report them under the conditions of approval.

Rehabilitation actions: 1. Restore

Restore estuarine habitat and connectivity.

Reinstate tidal channels and mangrove margins, remove temporary barriers and monitor water quality until it returns to baseline.

Sources