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Drysdale Hardyhead (Craterocephalus helenae)

The Drysdale hardyhead is a freshwater fish known from the Drysdale River in the Kimberley region of Western Australia. Its biology and site-level habitat requirements are poorly documented, so works near suitable freshwater habitat warrant careful assessment. It is DBCA Priority 2, a DBCA priority category and not a listing under the Biodiversity Conservation Act 2016.

Conservation status

Western Australia, WA Threatened and Priority Fauna List: Priority 2.

Seasonal considerations

No species-specific activity or breeding months are known. Use the following as a general planning reminder, not as a statement of seasonal biology.

Breeding period: Not documented.

Seasonal activity: Not documented.

Seasonal activity, movement and breeding timing are not documented for this species.

  • Works planning: General planning window only. No species-specific seasonal timing is known; assess risks and controls for the actual site and work period.

Identification: Appearance and size

Species-specific identification information is limited. Confirm any identification with a suitably qualified fish ecologist.

The Drysdale hardyhead is a freshwater hardyhead. No species-specific description of its appearance or size is documented.

Identification: Similar species

Craterocephalus marianae is a close relative. Craterocephalus helenae is distinguished from it by counts of midlateral scales, vertebrae and gill rakers. These features may require examination by a fish identification specialist.

Identification: Field signs

No reliable visual recognition cues or species-specific field signs are documented. A fish sighting alone may not confirm the species.

Distribution: Known range

The known range is in the Kimberley region of Western Australia, but the full distribution is not defined.

The Drysdale River is the known range. Atlas of Living Australia records show 19 Western Australian records at 10 distinct 0.1-degree locations, between latitude -15.7 and -14.4 and longitude 126.2 and 127. These record coordinates do not identify named sites.

Distribution: WA region and status

The DBCA list places the species in the Kimberley region and assigns it Priority 2. The category describes a poorly known species known from few locations, with some locations on conservation lands. No national listing is identified.

Habitat: Recorded setting

The species is associated with freshwater and the Drysdale River, but its preferred habitat within the river is not documented.

The species is known from the Drysdale River in the Kimberley. Records are not specified by reach, waterbody type or flow conditions.

Habitat: Site assessment

For project planning, assess freshwater habitats in and around the known range where works could affect aquatic habitat. This is a precautionary approach, not evidence that the species occupies every such site.

Foraging habitat: Reported diet

The species is reported to eat aquatic insects, small crustaceans and algae. Where and how it feeds are not documented.

No further dietary or foraging details are documented.

Foraging habitat: Implications for works

Avoid unnecessary disturbance to aquatic habitat and water quality where the species may occur. No particular feeding area or food resource has been identified for this species.

Breeding habitat: Known information

Breeding biology and breeding habitat are poorly known.

No breeding site, spawning behaviour, reproductive period, egg or young description, or breeding habitat is documented.

Breeding habitat: Precaution

Do not schedule works on the assumption that breeding is restricted to a particular season. Where aquatic habitat may be affected, seek advice from a fish ecologist before disturbance.

Sheltering habitat: Available evidence

Sheltering behaviour and refuge habitat are not documented.

No shelter type, refuge location, cover preference or response to disturbance is documented.

Sheltering habitat: Precaution

Do not assume that any particular channel feature or cover type is unoccupied. Minimise disturbance to aquatic habitat within the works footprint and adjacent areas that could be affected.

Threats: Threat information

No specific threats to the species have been identified.

The DBCA Priority 2 status reflects that the species is poorly known and known from few locations; it does not indicate that a particular threat has been confirmed.

Threats: Worksite risks to consider

As a precaution for freshwater works, assess whether the activity could disturb aquatic habitat or affect water quality or flow. These are general assessment considerations, not documented species-specific threats.

Survey methodology: 1. Desktop assessment

Species-specific detectability and survey methods are not documented. Plan surveys with a fish ecologist and do not treat a non-detection as proof of absence.

Check project locations against the known Drysdale River range, the Kimberley region listing and occurrence records. Confirm whether records are accurately located and relate to the work area.

Survey methodology: 2. Field assessment

Have a suitably qualified fish ecologist assess freshwater habitats that could be affected. Select survey methods and effort for the site and approvals, rather than assuming a species-specific method or detection rate.

Survey methodology: 3. Identification and records

Record survey conditions, locations and any fish observations. Seek specialist confirmation where identification is uncertain, as the taxonomic description notes a close relative and differences based on meristic counts.

Vegetation associations

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

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

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.

The species is known from the Drysdale River in the Kimberley.

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.

Habitat use: general

Attribution gap: No sentence-level reference is attached to the original profile block. Review the profile bibliography; this candidate is not source-verified.

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. Review and plan

Use the limited range information to guide a cautious, site-specific assessment before works begin.

Review occurrence information and assess whether the site or affected freshwater habitat is within the known Kimberley range. Records do not establish occupancy at every location in that range.

Before habitat disturbance: 2. Set controls

Define the work footprint and identify freshwater habitat that could be affected. Plan practical measures to limit unnecessary habitat disturbance and prevent avoidable changes to water quality or flow.

Before habitat disturbance: 3. Brief the crew

Explain that the species is poorly known and may not be reliably identified in the field. Set out who to contact if fish are observed or unexpected aquatic habitat is encountered.

During habitat disturbance: 1. Follow the work limits

Keep disturbance controlled and respond cautiously to fish observations or unexpected freshwater habitat.

Keep plant, access and other activities within the approved footprint. Apply the planned controls to minimise unnecessary disturbance to aquatic habitat and water quality.

During habitat disturbance: 2. Respond to observations

If fish are found in an area at risk from the works, pause the affected activity where safe and practicable, protect the area and contact the project ecologist. Field identification may be uncertain.

During habitat disturbance: 3. Manage unexpected conditions

If works encounter freshwater habitat or conditions that differ from the assessment, stop or limit the relevant activity as required by project procedures and obtain ecological advice before proceeding.

After habitat disturbance: 1. Inspect the affected area

Check that controls have been maintained and document observations or changes relevant to aquatic habitat.

Review the work area and adjacent freshwater habitat for unintended disturbance or changes requiring follow-up. No species-specific post-works inspection method is documented.

After habitat disturbance: 2. Record and report

Document fish observations, identification confidence, locations, work activities and any incidents. Refer records to the project ecologist and follow applicable reporting and approval requirements.

Rehabilitation actions: 1. Restore affected areas

No species-specific rehabilitation requirements are documented. Rehabilitation should respond to the freshwater habitat affected by the project.

Rehabilitate disturbed areas in accordance with project approvals and ecological advice, with the aim of limiting ongoing impacts to freshwater habitat.

Rehabilitation actions: 2. Monitor outcomes

Use site-specific monitoring to check whether rehabilitation objectives are being met. General rehabilitation success does not establish that the species is present or has recovered.

Sources