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Slender Carp Gudgeon (Hypseleotris ejuncida)

The Slender Carp Gudgeon is a small freshwater fish known from a limited part of the Prince Regent River system in the Kimberley, where it inhabits clear, quiet pools over sandstone. Its restricted known range makes careful assessment of suitable pools important before works.

Conservation status

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

Seasonal planning

Taxon-specific activity and breeding months are unknown. Plan surveys and works around site conditions and approvals rather than assuming a particular seasonal window.

Breeding season: Not recorded.

Seasonal activity: Not recorded.

Breeding months and other seasonal timing are unknown for this species.

  • Survey and works planning: General planning guidance only. No taxon-specific seasonal window is known; assess conditions and approvals at the site.

Identification: Appearance and size

Use the combination of body shape and markings for identification. Diagnostic field signs such as nests or tracks have not been documented.

A small, slender, tan gudgeon. It has three or four dark brown bars between the pectoral-fin base and the origin of the second dorsal fin, dark-edged scales forming a diamond pattern, a dark stripe below the middle of the side, a dark spot at the end of the caudal peduncle, and a dark bar across the pectoral-fin base.

It reaches around 6 cm standard length. Males are larger than females; females are generally paler and often have more distinct anterior body bands.

Identification: Similar species

Hypseleotris kimberleyensis is identified as a close relative. Features used to distinguish the Slender Carp Gudgeon include extensive scaling on the predorsal area and operculum, white spots and wavy bands on the second dorsal fin, wavy dark bands on the caudal fin, and a dark bar covering the pectoral-fin base.

Use an appropriate fish identification guide or seek specialist review where these features are unclear.

Identification: Field signs

No diagnostic field signs beyond the fish’s appearance are documented. A distinctive nest, spawning-site sign, or other sign that can be confirmed without observing the fish has not been described.

Distribution: Known range

The known distribution is very restricted in northern Western Australia. Records and descriptions differ in detail, so use mapped records as leads for assessment rather than a complete account of occupancy.

The species is reported from a small section of the Prince Regent River system in the Kimberley. Named records include Gundarara Creek, about 2 km upstream of its confluence with the Prince Regent River, and an unnamed tributary of the lower Prince Regent River.

Atlas of Living Australia records show 12 Western Australian records at four distinct 0.1-degree locations, between latitude -15.9 and -14.5 and longitude 125.3 and 126.7. Records outside WA were excluded as likely errors.

Distribution: WA listing and regions

The DBCA Threatened and Priority Fauna List dated 1 July 2025 includes the Slender Carp Gudgeon and flags the Kimberley region. It was added to the Priority Fauna List on 30 April 2024.

Habitat: Recorded habitat

The species is associated with a specific freshwater pool setting. Its use of other habitat types and broader habitat requirements are not documented.

It inhabits clear, quiet freshwater pools over sandstone, usually in or around crevices near the edge. Type specimens were collected from a clear, quiet pool over a sandstone bottom at depths to about 2 m.

Habitat: Site assessment

Check for clear, quiet pools with sandstone substrate and edge crevices within the Prince Regent River system. Whether the fish uses other waterbody types or how it responds to changes in flow, water quality, or pool conditions is unknown.

Foraging habitat: Recorded diet

The species’ diet is known, but its feeding locations and foraging behaviour have not been documented.

The Slender Carp Gudgeon feeds mainly on aquatic invertebrates.

Foraging habitat: Precaution for works

Do not assume that feeding is confined to one part of a pool. During assessment, consider the whole suitable pool and its margins. This is a precautionary approach, not a documented species-specific foraging pattern.

Breeding habitat: Recorded breeding

The species’ egg type and benthic spawning are known, but details of its breeding biology are limited.

The species is an oviparous benthic spawner. Its eggs are demersal and adhesive. FishBase reports direct pairing, a male-selected spawning site, and male guarding of eggs until hatching.

Breeding habitat: Limits of breeding information

Breeding months, egg numbers, and precise spawning microhabitat have not been documented. Avoid timing or designing works on the assumption that breeding is restricted to a particular season.

Sheltering habitat: Recorded shelter

Edge crevices are described as places where the fish is usually found. Other sheltering behaviour is not documented.

The species occurs in or around crevices near the edge of clear, quiet pools over sandstone. FishBase also describes rocky pools and crevices along shallow margins.

Sheltering habitat: Practical implication

Include pool margins and accessible crevices in site checks. Do not treat a pool as unsuitable solely because fish are not immediately visible in open water.

Threats: Information available

Specific threats to this species have not been identified. Its limited known distribution and Priority 2 status warrant a cautious approach, but do not establish a particular threat.

Impacts, population trends, and causes of decline have not been documented for this species.

Threats: Works risk

Where proposed works could affect a suitable pool or its margins, assess the risk before disturbance and seek appropriate ecological advice. This is a precaution based on the recorded habitat and restricted known range, not a documented species-specific threat.

Survey methodology: 1. Desktop assessment

A species-specific survey method and detection rate have not been established. Use qualified freshwater fish ecologists and suitable methods authorised for the site.

Review occurrence records, the proposed works footprint, and mapped water features. Confirm whether clear, quiet sandstone pools and pool-edge crevices may be affected, and check for records in or near the Prince Regent River system.

Survey methodology: 2. Field inspection

Inspect suitable pools, substrates, margins, and crevices. A general freshwater fish survey may use appropriate, permitted capture or observation techniques selected by a qualified ecologist for the site conditions. The most effective method for this species is unknown.

Survey methodology: 3. Record and report

Record survey locations, methods, conditions, effort, and any fish observations or captures. Photograph diagnostic features where practicable and arrange specialist identification if uncertain. Do not interpret a non-detection as proof of absence.

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

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

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

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. Confirm the work area

Plan works around the possibility that suitable pools and their margins may support the species, even where surveys have not confirmed its presence.

Map water features and identify clear, quiet freshwater pools over sandstone, including edge crevices, within or near the proposed footprint. Review known Prince Regent River system records and obtain ecological advice where suitable habitat may be affected.

Before habitat disturbance: 2. Set precautions

Where feasible, avoid direct disturbance to suitable pools and margins. Brief the crew on the habitat description, the fish’s key identification features, and the requirement to pause work and notify the environmental lead if an unfamiliar small fish is observed.

During habitat disturbance: 1. Protect pools and margins

Avoid unnecessary disturbance to suitable freshwater pools and their edge habitats while works are underway.

Keep machinery, spoil, sediment, and other work materials out of identified suitable pools and their margins where practicable. Avoid damage to sandstone substrates and edge crevices.

During habitat disturbance: 2. Respond to observations

If fish are observed in an affected area, pause the relevant work, prevent further disturbance, and contact the environmental lead and a qualified freshwater fish ecologist. Do not capture or move fish unless this is undertaken by appropriately authorised personnel under the applicable approvals.

After habitat disturbance: 1. Inspect the site

Check that work controls have been effective and document any changes to suitable pool habitat or fish observations.

After works, inspect any nearby suitable pools and margins for visible damage, sediment deposition, or other changes associated with the works. Record observations and report unexpected impacts through the project’s environmental process.

After habitat disturbance: 2. Retain records

Keep survey results, field observations, photographs, and incident records with the project documentation. Seek ecological advice if the works may have affected suitable habitat.

Rehabilitation actions: 1. Protect habitat conditions

A species-specific rehabilitation method has not been established. Prioritise preventing damage to the recorded pool habitat and seek site-appropriate ecological advice if rehabilitation is needed.

Avoid further disturbance to clear, quiet freshwater pools, sandstone substrates, and pool-edge crevices. Do not introduce materials or alter pool features without assessing the likely effects and obtaining appropriate advice.

Rehabilitation actions: 2. Monitor outcomes

If rehabilitation is required, document the measures taken and check for visible changes to the affected pool and margins. A species-specific rehabilitation target or monitoring period has not been established.

Sources