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Dwarf Sawfish (Pristis clavata)

The dwarf sawfish is a shark-like ray of shallow coastal waters, estuaries and the tidal reaches of rivers across northern Australia, from the Pilbara and Kimberley to the Gulf of Carpentaria and western Cape York. It is Vulnerable and listed migratory under the EPBC Act, Vulnerable in the Northern Territory and Priority 1 on the WA list. The Kimberley, especially King Sound and the Fitzroy River estuary, is its main known stronghold.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

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

Western Australia, WA Threatened and Priority Fauna List: Priority 1. DBCA lists this species as specially protected migratory fauna and retains this Priority category alongside it.

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

Late dry season use of the upper Fitzroy River estuary recorded by acoustic tracking. Timing in other rivers is unknown.

Breeding mode: Live young.

Timing varies between rivers and years.

  • Juveniles concentrated in upper estuary pools (Fitzroy River): Late dry season use of the upper Fitzroy River estuary recorded by acoustic tracking. Timing in other rivers is unknown.

Identification: Appearance and size

A sawfish with a short, wide saw carrying 18 to 24 evenly spaced rostral teeth, according to the Florida Museum species account.

A sawfish with a short, wide saw carrying 18 to 24 evenly spaced rostral teeth, according to the Florida Museum species account.

Identification: Similar species

It shares estuaries with the freshwater and green sawfish. Tooth count and spacing, saw shape and fin position separate them. Photograph the saw from above if one is seen.

Distribution: Australian range

Recorded from about Port Hedland in the Pilbara through the Kimberley and Northern Territory to the Gulf of Carpentaria and western Cape York. The FRDC report notes distinct genetic stocks in WA, the northern NT coast and the Gulf of Carpentaria.

Recorded from about Port Hedland in the Pilbara through the Kimberley and Northern Territory to the Gulf of Carpentaria and western Cape York. The FRDC report notes distinct genetic stocks in WA, the northern NT coast and the Gulf of Carpentaria.

Distribution: Western Australia

In WA it is known from King Sound and the Fitzroy, May, Robinson and Pentecost Rivers, among other tidal systems. It probably occurs in other inadequately surveyed rivers.

Habitat: Estuary and coastal habitat

Shallow coastal and estuarine waters, mudflats, mangrove creeks and tidal river reaches. The DCCEEW report card notes it rests in mangroves at high tide and is active on mud and sand flats while the tide is moving.

Shallow coastal and estuarine waters, mudflats, mangrove creeks and tidal river reaches. The DCCEEW report card notes it rests in mangroves at high tide and is active on mud and sand flats while the tide is moving.

Lear et al. (2021) found juveniles in the Fitzroy River estuary used a large pool near the tidal limit in the late dry season (August to November), then moved closer to the river mouth and King Sound in the wet and early dry seasons.

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

Popeye mullet (Rhinomugil nasutus), other bony fish and prawns, taken close to the bottom.

Popeye mullet (Rhinomugil nasutus), other bony fish and prawns, taken close to the bottom.

Breeding habitat: Breeding and nurseries

The DCCEEW report card notes it breeds in estuarine or fresh waters in the wet season, with pupping possibly running to the start of the dry season. Estuaries such as the Fitzroy act as nurseries where juveniles may stay for at least three years.

The DCCEEW report card notes it breeds in estuarine or fresh waters in the wet season, with pupping possibly running to the start of the dry season. Estuaries such as the Fitzroy act as nurseries where juveniles may stay for at least three years.

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

Sheltering habitat: Shelter

Inundated mangrove forest at high tide, and deeper estuarine pools in the late dry season.

Inundated mangrove forest at high tide, and deeper estuarine pools in the late dry season.

Threats: Threats

DCCEEW names entanglement in fishing nets, because the saw is easily caught, as the greatest threat after habitat loss. Sawfish are also killed for their fins and saws.

DCCEEW names entanglement in fishing nets, because the saw is easily caught, as the greatest threat after habitat loss. Sawfish are also killed for their fins and saws.

Barriers, changes to flow and salinity, and loss of mangroves and tidal flats affect the estuarine nurseries.

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, mudflats, mangrove creeks and tidal river reaches.

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.

Shallow coastal and estuarine waters, mudflats, mangrove creeks and tidal river reaches.

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