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Pouched Lamprey (Geotria australis)

The Pouched Lamprey is a jawless, eel-shaped fish that uses freshwater rivers and streams for its larval and breeding stages, with a marine phase between them. River works may affect muddy larval habitat or obstruct migrations, so care is warranted at waterways. In Western Australia, DBCA lists the species as Priority 3.

Conservation status

Western Australia, WA Threatened and Priority Fauna List: Priority 3.

Seasonal activity

Upstream migration is reported during winter and spring, while young lampreys move downstream to the ocean during winter, often during high flows. Exact WA months and precise spawning dates are not known.

Upstream movement: Reported during winter and spring.

Downstream movement: Young lampreys migrate towards the ocean during winter, with high-flow periods reported.

Seasonal information describes winter and spring, not specific calendar months. Plan checks around local weather and flow conditions as well as the seasonal information.

  • Upstream migration: Winter and spring migration are reported, but the encoded months are not specified.
  • Downstream movement of young: Winter movement during high-flow periods is reported, but the encoded months are not specified.
  • Works planning: Planning window only. Check waterways before works in any season because local timing and detectability are not established.

Identification: Appearance and size

Look for a jawless, eel-shaped fish with a sucker-like oral disc. Its appearance changes substantially between larval, marine and freshwater adult stages.

Adults have a cartilaginous skeleton, seven pairs of pore-like gill openings, a single nostril on top of the head and no paired fins or scales. The mouth forms a suctorial disc lined with rasping teeth.

Adults grow to about 600 mm. Larvae, called ammocoetes, are brown, worm-like and blind. Juveniles and ocean-going sub-adults are described as silvery blue; adults entering rivers are dark bluish to brownish above and silvery below. Mature or maturing males develop a pouch beneath the head.

Adult length: Up to about 600 mm

Larval appearance: Brown, blind and worm-like

Identification: Similar species

Similar species in Western Australia have not been identified. Do not identify an animal as a Pouched Lamprey from its eel-like shape alone; check for the jawless oral disc and the paired rows of gill openings.

Identification: Field signs

Larvae may be present in soft stream sediments, but there is no reliable field sign for detecting them without disturbance. Migrating lampreys may be seen below natural or artificial barriers, and adults may move at night in wet conditions.

Distribution: Known range

In WA, records are concentrated in rivers and streams of the south-west, with records reported more broadly along the south coast.

WA records are reported from many rivers between Perth and Albany, including the Swan, Canning, Serpentine, Capel, Carbunup, Margaret, Blackwood, Donnelly, Warren, Walpole and Goodga systems. Records are sporadic, particularly outside the south-west corner from Capel to Denmark.

Atlas of Living Australia records show 70 WA records at 30 distinct 0.1-degree locations, from latitude -35.1 to -20.6 and longitude 115.7 to 121.9. These coordinates describe the record envelope, not specific survey locations.

Distribution: WA regions and status

The DBCA list flags the Wheatbelt, South Coast, Swan, South West and Warren regions. The species is listed as Priority 3, described as poorly known, known from several locations and not under imminent threat. This is a DBCA priority category, not a listing under the Biodiversity Conservation Act 2016. No national listing is given.

Distribution: Wider distribution

The species is recorded from southern Australia, including Tasmania, New Zealand and parts of South America. In Australia, its range extends along the south coast from the Gippsland Lakes to the Moore River north of Perth.

Habitat: Freshwater reaches

The species uses freshwater, estuarine and marine environments at different stages of its life cycle. The clearest habitat information relates to freshwater streams and their sediments.

Adults spawn in freshwater rivers and streams, usually in small, shallow streams with gravel bottoms. Larvae occupy soft muddy or sandy stream sediments, including upper reaches of coastal streams.

Habitat: Connected waters

After metamorphosis, young lampreys migrate downstream to estuaries and coastal waters before spending a marine phase at sea. The species has an anadromous life cycle, with adults returning to freshwater to breed.

Foraging habitat: Larval feeding

Feeding habitat differs between the larval and marine stages. Adults returning to freshwater to spawn stop feeding.

Ammocoetes live in sediment burrows and filter-feed on microscopic material from the water above. Their food includes detritus, microscopic algae, plankton and suspended organic matter.

Foraging habitat: Marine feeding

After metamorphosis, young lampreys move to marine waters and feed parasitically on other fishes, attaching with the oral disc and rasping flesh. Particular host fish have not been identified.

Foraging habitat: Return migration

Adults stop feeding when they return to freshwater and rely on stored reserves during migration and spawning.

Breeding habitat: Spawning reaches

Breeding takes place in freshwater, and adults die shortly after spawning. Preserve access to suitable stream reaches and avoid disturbing potential spawning substrates.

Spawning occurs in small, shallow, gravel-bottomed streams. Eggs are reported in clusters beneath boulders. The female prepares a small depression in the substrate.

Breeding habitat: Adults and eggs

The male attaches to the female and wraps around her during spawning. Males use the gular pouch and ventral surface to groom eggs and newly hatched larvae, which may help oxygenate the eggs.

Clutch size and precise spawning dates in WA are not known.

Sheltering habitat: Larval burrows

Larvae shelter in sediment burrows. Daytime refuges for migrating lampreys are also reported, but specific refuge requirements are not established.

Ammocoetes burrow into soft muddy or sandy stream sediments. Avoid unnecessary excavation, dewatering or sediment disturbance in suitable stream reaches.

Sheltering habitat: Daytime cover

Lampreys may hide during daylight under rocks and logs and among fringing vegetation. Treat these features as potential cover during works near streams.

Threats: Barriers and migration

Barriers to migration and changes to river conditions are concerns for lamprey populations.

Dams, weirs and other obstructions can impede upstream movement. Lampreys may be injured or exhausted while negotiating obstacles, and may become stranded when following runoff flows away from the water.

Threats: River changes

Concerns include river regulation, climate change, predation by invasive trout and habitat loss associated with clearing of natural bushland. Works that alter flow, sediment or streamside cover warrant care.

Survey methodology: 1. Desktop assessment

A standardised survey protocol and detection probabilities have not been established. Use non-destructive checks and seek advice where suitable habitat or migrating animals may be affected.

Review available records and identify waterways, stream sediments, barriers and potential connections to estuarine or coastal waters. Check the DBCA regional listing and records for the project area. Do not assume the species is absent because no records are mapped.

Survey methodology: 2. Habitat inspection

Walk accessible stream margins and inspect the proposed works footprint without disturbing sediment, rocks, logs or vegetation. Record waterway condition, soft sediment reaches, gravelly shallow sections and barriers.

Survey methodology: 3. Timing and observations

Upstream movement is reported during winter and spring, often on dark, wet nights when water levels are rising. Where practicable, check for lampreys near barriers and work areas before night-time or high-flow works. Do not use unapproved capture methods.

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.

Adults spawn in freshwater rivers and streams, usually in small, shallow streams with gravel bottoms.

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, VIC, TAS, SA, NSW.

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. Confirm constraints

Plan works around waterways and migration pathways, and do not rely on a single survey to rule out the species.

Review records, waterway connections, proposed clearing and the location of barriers. Have a suitably qualified ecologist assess whether the footprint could affect stream habitat or lamprey movement.

Before habitat disturbance: 2. Set work controls

Mark no-go areas around waterways and retain streamside vegetation where possible. Plan to limit sediment mobilisation, changes to flow and obstruction of channels. Schedule in-channel or barrier-related work to minimise the chance of trapping or blocking migrating fish.

Before habitat disturbance: 3. Brief crews

Explain how to recognise the jawless oral disc and gill openings, and instruct crews to stop work and contact the fauna spotter catcher or ecologist if a lamprey is found.

During habitat disturbance: 1. Protect the waterway

Keep work methods conservative near water and respond promptly to any lamprey or unexpected change in stream conditions.

Keep machinery, spoil and materials out of the channel and stream sediments unless the approved scope requires otherwise. Use sediment and runoff controls, and avoid creating new routes that could draw migrating lampreys away from the water.

During habitat disturbance: 2. Check before working

Before disturbing stream margins or working near barriers, check the immediate area for animals, especially during wet conditions and periods of rising water. Avoid turning rocks or excavating sediments unless necessary and authorised.

During habitat disturbance: 3. Stop and escalate

If a lamprey is found in the work area, pause the activity, protect it from handling and drying, and contact the fauna spotter catcher or ecologist for advice under the project’s approved procedures. Record the location and circumstances.

After habitat disturbance: 1. Inspect the work area

Check that works have not left barriers, stranded animals or avoidable damage to stream habitat.

After works, inspect affected stream margins and access routes for stranded animals, blockages, disturbed sediment and displaced cover. Report any lamprey observations to the project ecologist.

After habitat disturbance: 2. Record and respond

Document observations, conditions and corrective actions. If a migration route or stream habitat has been affected, notify the responsible environmental lead and implement the approved response.

Rehabilitation actions: 1. Restore stream margins

Rehabilitation should restore waterway function and suitable streamside conditions without introducing new barriers or sediment impacts.

Stabilise disturbed banks and reinstate appropriate streamside vegetation. Use methods that limit erosion and avoid adding fine sediment to stream reaches.

Rehabilitation actions: 2. Maintain passage

Remove temporary obstructions when safe and authorised, and confirm that the channel remains open to fish movement. Monitor the rehabilitated area for erosion, runoff pathways or new barriers.

Sources