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Australian Grayling (Prototroctes maraena)

The Australian Grayling is a small, diadromous fish that spends most of its life in freshwater coastal rivers, with larvae and juveniles using estuarine and marine waters. It is vulnerable to fish passage barriers, altered flows, sediment, poor water quality and construction impacts, so waterways connected to the sea should be treated as potential habitat on development sites.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

Victoria, Flora and Fauna Guarantee Act 1988: Vulnerable.

Tasmania, Threatened Species Protection Act 1995: Vulnerable.

Breeding season

Timing varies between catchments and depends on flow and temperature. The pattern below is a practical south-eastern Australian guide, not a substitute for local records and flow data.

The February to May survey window is identified as suitable for detecting the species in Victoria because migratory fish are more likely to be collected at lower flows. Avoid assuming that a dry or low-flow survey represents year-round absence.

  • Breeding and spawning: Spawning occurs from late summer to winter, with examples of peak activity in April and May. Local timing responds to increased flow and falling water temperature.
  • Larvae in downstream and coastal habitat: Eggs hatch after 10 to 20 days. Buoyant larvae drift downstream, and larvae or juveniles use estuarine and marine waters for about 6 months. The exact period varies between rivers.
  • Juvenile return upstream: In Victorian examples, juveniles return to freshwater at about 6 months of age, with upstream movement occurring around November.
  • Adult freshwater residence: Most of the life cycle is spent in freshwater rivers and streams. Adults may make local movements of less than 5 km outside the spawning period.
  • Highest clearing risk: Disturbance is most likely to harm the species from February to June, when spawning, egg development, downstream larval movement and flow-sensitive migration may overlap. November also carries risk because juveniles may be moving upstream.

Identification

Australian Grayling is a slender, laterally compressed fish with soft-rayed fins and a small conical head. Identification can be difficult for juveniles because they may occur in mixed schools with other small native fish.

Adults are generally greyish bronze, olive or brown on the back, silvery on the sides and pale underneath. The body has very thin, easily dislodged scales, the head is scaleless and there is no lateral line.

The mouth is small and slightly oblique, with the lower jaw shorter than the upper jaw. The species has large eyes, a rounded snout, an adipose fin and soft fins without spines.

Common length: 170 to 190 mm

Maximum recorded size: About 330 mm and 0.5 kg

Distinctive odour: A cucumber-like odour may be released by freshly caught fish

Identification: Separating similar fish

Juvenile Australian Grayling can resemble smelts, mullets and hardyheads. These fish may occur together during upstream whitebait runs, so a mixed school should not be identified by appearance alone.

Check the combination of a scaleless head, absent lateral line, thin deciduous scales, soft-rayed fins, small oblique mouth and shorter lower jaw. The cucumber-like odour is a useful supporting feature only when the fish has already been captured.

  • Do not rely on body colour alone, especially for juveniles.
  • Keep handling brief and use wet hands because the scales are easily lost and the fish is sensitive to stress.
  • Use a qualified fish ecologist or the relevant threatened fish survey guidance where identification is uncertain.

Identification: Sex and field signs

The species is sexually dimorphic during the breeding season. Mature males develop small nuptial tubercles on the scales and on the pectoral, pelvic, dorsal and anal fin rays.

There are no reliable terrestrial field signs such as tracks, scats, calls, nests, burrows or eyeshine. Presence is normally established by targeted fish sampling, records or observation of suitable connected habitat.

  • Treat cool, flowing coastal streams connected to estuaries as potential habitat even when fish are not seen.
  • Record fish condition, size, location, waterway, flow conditions and capture method.
  • Minimise time out of the water and keep captured fish in a container of water while being identified.

Distribution: National range

Australian Grayling occurs in coastal catchments of south-eastern Australia. Its distribution includes freshwater, estuarine and marine reaches, and it may travel more than 300 km upstream in suitable connected systems.

In New South Wales, the historical range extended from the Hunter River south to the Victorian border, with more recent records concentrated on the south coast from the Shoalhaven River towards the border.

In Victoria, the species has been recorded in coastal rivers from the Hopkins River eastwards, including the Barwon, Yarra, Tarwin, Tambo, Mitchell, Snowy, Bemm, Thomson and Latrobe systems.

In Tasmania, records occur in catchments draining to the north, west and east coasts, including the Mersey, Gawler, Leven, Tamar, North Esk, Great Forester, Derwent and Huon rivers. It has also historically occurred on King Island.

South Australian records are rare. A verified record was made at Ewens Ponds in 1982, while other records remain unverified or may represent vagrant fish from Victorian populations.

Main mainland range: From the Shoalhaven River in New South Wales to the Hopkins River system in western Victoria

Historical northern extent: Coastal catchments as far north as the Hunter River, with some historical accounts extending north of Sydney

States and territories with records: New South Wales, Victoria, Tasmania and South Australia

Distribution: Strongholds and local populations

Historically strong Victorian populations were recorded in the Tambo, Mitchell, Tarwin and Yarra catchments. The Tarwin River is identified as an important river for the species, and the Glenelg River has produced recent verified records after more than 100 years without a confirmed record.

The Mersey River is described as a significant Tasmanian stronghold. Locally abundant fish have also been recorded at times in the Gawler, Leven, Tamar, North Esk and Great Forester rivers, with significant numbers sometimes present in the lower Derwent and Huon rivers.

The species can recolonise some rivers when fish passage is restored. For example, a fishway at Dights Falls has enabled movement into parts of the Yarra from which the species had been absent for decades.

Distribution: Population size and trend

There is no reliable national population estimate. Records and survey results indicate a contracted and fluctuating distribution, with recruitment and local abundance strongly affected by river flow and connectivity.

In New South Wales, the historical distribution was estimated to have contracted by 65 percent between observations from 1994 to 2014. Surveys from 2008 to 2012 detected one individual at 1 of 113 sites, compared with 64 individuals at 22 sites in surveys from 1993 to 1995.

A Victorian assessment inferred 5,000 to 10,000 mature individuals, but this estimate is uncertain. The Australian Government assessment identified continuing risks from barriers, habitat degradation, altered flow and climate change.

NSW distribution contraction: 65 percent based on observations from 1994 to 2014

Recent NSW survey result: 1 individual from 113 sites surveyed from 2008 to 2012

Inferred mature population: 5,000 to 10,000 individuals, with uncertainty

Habitat: Freshwater habitat

The species depends on connected coastal river systems that provide freshwater adult habitat and access to estuarine and marine areas. Habitat use can vary between catchments, and absence from a particular reach during a survey does not demonstrate that the reach is unused.

Adults generally use cool, clear, moderately flowing rivers and streams with gravel beds and alternating pools and riffles. Instream snags, shaded margins and stable banks can add cover and habitat complexity.

The species can also occur in turbid, muddy-bottomed and heavily silted reaches, including parts of the Tarwin River. It may penetrate well inland, with records more than 300 km upstream from the sea.

  • Retain natural river channels, pools, riffles, gravel beds, snags, banks and riparian shading.
  • Maintain a continuous aquatic pathway between occupied reaches, estuaries and the sea.
  • Treat both permanent and intermittently connected coastal streams as potential habitat.

Habitat: Water and landscape setting

The species is associated with coastal drainages on the eastern and southern flanks of the Great Dividing Range. It is absent from the inland Murray-Darling system according to the cited distribution assessment.

Water temperature, flow velocity, seasonal flow events, salinity and river mouth condition affect movement, spawning and recruitment. Construction near a waterway can therefore affect habitat downstream even when works remain outside the main channel.

  • Protect riparian vegetation and avoid exposing banks and floodplain soils to erosion.
  • Keep sediment, concrete washout, fuels, oils and other pollutants out of the channel and floodplain.
  • Plan works around rainfall and flow events because floodplain earthworks can mobilise sediment into downstream habitat.

Foraging habitat: Diet

Australian Grayling is an omnivorous benthic and water-column feeder. It forages in freshwater pools, riffles and margins, and may take prey from the water surface.

The diet includes aquatic insect larvae, other aquatic insects, small crustaceans, gastropods, algae, macrophytes and other plant material. Terrestrial insects falling onto the water surface are also eaten.

Stomach observations indicate that insect larvae can form a major part of the diet. Fish have been observed feeding from algae-covered rocks and rising to insects in large still pools.

Main prey: Aquatic insect larvae and other aquatic insects

Other food: Small crustaceans, gastropods, algae, macrophytes and terrestrial insects

  • Retain algae-covered rocks, gravel riffles, pools and overhanging vegetation that support aquatic and terrestrial prey.
  • Prevent fine sediment, nutrient enrichment and turbidity from smothering rocks, macrophytes and benthic prey habitat.
  • Avoid removing riparian cover that supplies shade and falling terrestrial insects.

Foraging habitat: Foraging area

No reliable home-range distance is provided. Adults may make local movements of less than 5 km outside the spawning period, but their feeding habitat is connected to a much larger river system used during annual migration.

For site assessment, consider the channel, banks, pools, riffles, snags, riparian edge and immediately downstream reaches as part of the foraging habitat.

Breeding habitat: Breeding biology

Breeding depends on access between freshwater and the lower river or estuary, suitable flow cues and low enough salinity for eggs to develop. Most individuals probably spawn only once.

Adults generally move downstream to lower freshwater reaches above the estuary, where spawning aggregations form. Spawning timing varies between catchments and is usually associated with increased flow and falling water temperature, sometimes with changes in day length.

Eggs are demersal, non-adhesive and less than 1 mm in diameter. They may settle on gravel, granite, mud or silt. Hatching occurs after 10 to 20 days, and buoyant larvae are swept downstream into estuarine and marine habitat.

Larvae and juveniles use coastal waters for about 6 months before juveniles return upstream to freshwater, generally around November in Victorian examples.

Breeding season: Late summer to winter, commonly February to May in Victorian survey guidance, with local timing varying

Egg number: 25,000 to 68,000 eggs per female, averaging about 47,000

Egg size and incubation: Less than 1 mm; hatch after 10 to 20 days

Age at maturity: Males at 1 to 2 years; females generally after 2 years

Adult life span: Most die after the second or third year; some survive to 4 or 5 years

Larval and juvenile phase: About 6 months in estuarine or marine waters before upstream return

  • Maintain unimpeded upstream and downstream passage through the full river to estuary connection.
  • Protect spawning reaches from sediment pulses, salinity increases, dewatering, pollutants and artificial light at night.
  • Avoid disturbing channel margins, pools and riffles during flow-triggered spawning movements.

Breeding habitat: Breeding habitat features

Spawning habitat is in freshwater reaches above the estuary, but successful recruitment requires the whole connected pathway from spawning reach to coastal nursery waters and back upstream.

Flow duration matters because larvae must drift to coastal waters and juveniles must later return to freshwater. Eggs do not hatch as salinity increases, so changes to estuarine salinity and river mouth connectivity can affect recruitment.

  • Do not install weirs, culverts, temporary crossings, bunds or other structures that obstruct fish passage.
  • Keep sediment controls functional through rainfall and high-flow events.
  • Avoid night lighting near channels during spawning and downstream larval movement where practicable.

Sheltering habitat: Adult and juvenile cover

Specific refuge structures and dimensions have not been established. The best-supported approach is to retain the physical features used by adults, juveniles and larvae for cover, flow refuge and movement.

Adults use pools, riffles, flowing runs, gravel beds, snags, shaded margins and undercut or structurally complex banks. Juveniles returning from coastal waters use connected freshwater reaches and may occur in mixed whitebait schools.

Newly hatched larvae are buoyant and are transported downstream by river flow. They are strongly responsive to light and prefer shaded conditions.

  • Retain instream snags, pool and riffle sequences, gravel habitat, bank cover and riparian shade.
  • Do not enter the channel, disturb banks or remove snags unless authorised and assessed for threatened fish impacts.
  • Use low-impact lighting and shield lights from the channel during night works.

Sheltering habitat: No known terrestrial refuges

The species does not use nests, hollows, dens, burrows or terrestrial roosts. Its refuge and shelter requirements are aquatic and include suitable flow, depth, shade, substrate and cover.

Threats: Clearing and construction

The main project risks are loss of river connectivity, altered flow, sediment and poor water quality. Indirect impacts can affect fish downstream even when machinery and structures remain outside the channel.

Riparian and floodplain clearing can remove shade and cover, destabilise banks and increase sediment loads. Earthworks for roads, bridges, services and floodplain infrastructure can discharge sediment, nutrients, concrete, fuel or oil into the river.

Temporary crossings, bunds, cofferdams, culverts and poorly designed bridge structures can obstruct movement or change floodplain flow paths. Construction disturbance and artificial lighting may also affect movement during breeding and larval migration.

Example construction buffer: The Tarwin River assessment specified a 5 m buffer from the channel for protection and exclusion controls

Example monitoring frequency: Weekly during construction, with additional sampling during rain events

  • Keep works, spoil, fuel, oil and machinery outside the channel and above the 1 in 100 year flood level where practicable.
  • Establish exclusion fencing and sediment controls for earthworks within 5 m of the river channel.
  • Minimise the construction footprint and reinstate disturbed banks and floodplain vegetation immediately after works.
  • Monitor turbidity, electrical conductivity, pH, dissolved oxygen, temperature, rainfall, visible oil and litter before and during works.
  • Stop or secure floodplain works when forecast rainfall or river levels could mobilise sediment or inundate work areas.

Threats: Barriers and hydrology change

Weirs, dams, locks, barrages and tidal barriers restrict upstream and downstream movement. The species has become locally extinct above some barriers, including Tallowa Dam in the Shoalhaven River.

Water extraction, river regulation, drought and altered seasonal flows can remove spawning cues, reduce larval transport and prevent juvenile return. River mouth closure can also block movement between freshwater, estuary and sea.

  • Maintain or restore fish passage through permanent and temporary waterway structures.
  • Avoid taking water or changing flow during periods when spawning and migration depend on freshes or falling temperatures.
  • Assess downstream and estuarine effects, not just the footprint of the works.

Threats: Fire, introduced fish and disease

Drought, higher water temperatures and altered rainfall can reduce habitat and recruitment. Bushfire and post-fire rainfall can add ash, nutrients and sediment to waterways, with sediment slugs documented as travelling up to 80 km downstream of fire-affected areas.

Brown Trout, Rainbow Trout and Redfin can prey on or compete with Australian Grayling. Carp can increase turbidity, damage macrophytes and erode banks, while Eastern Gambusia can prey on eggs and larvae.

Known or suspected health threats include Anchor Worm, trematodes, fungal disease such as Saprolegnia, and pathogens associated with introduced fish. Incidental recreational and whitebait fishery capture remains a further pressure.

Post-fire sediment reach: Sediment slugs may affect aquatic ecosystems up to 80 km downstream

Handling sensitivity: Thin, deciduous scales make the species particularly prone to handling stress

  • Inspect waterways downstream of recent fire areas for sediment, ash, nutrient and water-quality impacts.
  • Prevent the movement of introduced fish, water, equipment and disease between catchments.
  • Do not target, retain or handle Australian Grayling unnecessarily during fish surveys or recreational fishing.
  • Use approved decontamination, fish handling and release procedures for all aquatic equipment.

Survey methodology: 1. Establish the survey area and habitat context

Survey Australian Grayling where works may affect coastal rivers, streams, estuaries, floodplains or tributaries with a current or historical connection to the sea. Survey the full area that could be affected, including downstream habitat and any barriers or temporary works that could alter fish movement.

  • Map the project footprint, upstream and downstream reaches, tributaries, wetlands, estuary connections, river crossings and any areas that could receive sediment or altered flows.
  • Check state databases, the Australian Faunal Directory, the Protected Matters Search Tool, Species Profile and Threats Database, recovery information, published records, local fish experts and community observations.
  • Assess whether the waterway provides resident freshwater habitat, downstream spawning habitat, larval drift habitat, juvenile return habitat or a movement pathway between these areas.
  • Give particular attention to cool or clear streams with alternating pools and riffles and gravel substrates, while also considering turbid or heavily silted habitat because Australian Grayling can occur there.

Survey methodology: 2. Time the survey to improve detection

Preferred Victorian survey period: December to April

Typical spawning period: Late summer to winter, with timing varying by river and annual conditions

Juvenile return period reported for Victorian populations: About November

  • In Victoria, preferentially survey from December to April, when flows are generally lower and migratory fish are more likely to be collected.
  • Plan additional surveys where one visit cannot represent the fish assemblage or where flows, rainfall or seasonal migration are likely to affect detection.
  • Avoid drawing conclusions from a negative result when habitat is suitable, the waterway is intermittently connected, access is poor, or survey conditions prevent effective sampling.
  • Record recent rainfall, flow conditions, water temperature, turbidity, conductivity, dissolved oxygen and any temporary disconnection from the estuary.

Survey methodology: 3. Use fish-specific sampling methods

Example targeted survey period: 25 to 27 April 2018

Example survey coverage: Seven sites on a river west branch and one site on the main river

Example catch result: Three Australian Grayling, including two young of the previous year and one approximately two-year-old fish

  • Use a combination of suitable methods because detection depends on access, depth, flow, habitat and salinity.
  • Use boat, bank or backpack electrofishing where conditions and permits allow, selecting the equipment suited to the channel and depth.
  • Supplement electrofishing with fyke nets, bait traps, fine mesh seines or dip-netting where appropriate, noting that traps and dip-netting may be less suitable for Australian Grayling detection than electrofishing.
  • Apply the Australian Government survey guidelines for threatened fish and use appropriately trained and authorised operators.
  • For a project-level example, a targeted survey sampled eight sites over three days and two nights, using 603 seconds of boat electrofishing, 1,550 seconds of bank electrofishing, 765 seconds of backpack electrofishing, 91 fyke-net hours and 292 bait-trap hours.
  • Keep fish in water or a container of water for the minimum time needed for identification and release, and handle them with wet hands because their scales are easily lost and the fish are sensitive to stress.

Survey methodology: Minimum effort and reporting

  • Prepare a written survey design that states the site boundaries, habitat types, seasons, flow conditions, methods, effort at each site, detection limitations and the basis for concluding presence or absence.
  • Survey all suitable reaches within and downstream of the project area that could be affected by sediment, pollutants, altered flows, barriers, lighting or bank disturbance.
  • Record each capture or observation with date, time, coordinates, waterway, habitat, life stage or size, method, effort, photographs where permitted, and release location.
  • Use wet hands and minimise handling, and ensure electrofishing, trapping, animal ethics, fisheries and threatened species permits are in place before fieldwork.
  • Submit verified records to the relevant state wildlife or biodiversity database and provide records and survey results to the approval authority where required.
  • Treat the species as present when suitable habitat and reliable regional records occur, even if a targeted survey does not detect it.

Before habitat disturbance: 1. Avoid and minimise habitat disturbance

Australian Grayling depends on connected freshwater, estuarine and marine habitats. Before works begin, prevent barriers, sediment release and changes to flow from interrupting movement, spawning or recruitment.

  • Keep works, access tracks, stockpiles, refuelling areas and compounds out of the channel, banks, riparian zone and floodplain wherever practicable.
  • Retain pools, riffles, gravel or muddy substrates, instream cover, snags, shaded banks, riparian vegetation and connections to tributaries and the estuary.
  • Do not install or leave temporary crossings, bunds, cofferdams, pipes, screens or other structures that block upstream or downstream fish movement.
  • Maintain the natural channel, flow path and connection between freshwater, brackish and marine reaches.
  • Design crossings and temporary works to avoid barriers to migration and to prevent sediment, road runoff, oils and other pollutants entering the waterway.

Before habitat disturbance: 2. Confirm approvals and plan the works

EPBC Act status: Vulnerable

Victorian and Tasmanian status supplied for this profile: Vulnerable

Example construction timing recommended for Tarwin River floodplain works: December to March

  • Check whether the action may significantly affect this EPBC Act listed species or its habitat and make an EPBC Act referral or obtain the required approval where applicable.
  • Confirm state threatened species, fisheries, animal ethics, scientific collection, waterway and works-on-waterways permits before work starts.
  • Prepare a fauna and aquatic habitat management plan that identifies Australian Grayling habitat, movement pathways, exclusion areas, water quality limits, incident responses and qualified personnel.
  • Stage earthworks outside the locally relevant spawning and migration period where practicable, using local flow, temperature and rainfall information to refine the timing.
  • Use the December to March lower-rainfall period as an example construction window for floodplain works in the Tarwin River project, but set timing for the actual catchment and approvals.
  • Plan works so that fish passage is maintained continuously, including during floods, low flows and temporary diversion.

Before habitat disturbance: 3. Prepare and mark the site

  • Complete the pre-clearance aquatic habitat inspection and targeted fish survey before finalising the work footprint.
  • Mark no-go areas around the channel, banks, riparian vegetation, pools, riffles, tributaries, wetlands and any fish passage structures.
  • Use exclusion fencing and sediment fencing to keep machinery, spoil and people out of protected areas, including a five metre river-channel buffer where that requirement is adopted in the approved project plan.
  • Collect at least four weekly baseline water quality samples before establishment where the project may affect the waterway.
  • Install weather, rainfall and upstream flow monitoring, and establish upstream and downstream water quality sites before construction.

During habitat disturbance: 1. Apply daily controls

Manage the site as though Australian Grayling is present wherever suitable habitat occurs. The fauna spotter catcher supports the aquatic specialist and machinery operators, but must not substitute for licensed fish capture or waterway supervision.

  • Hold a daily pre-start briefing covering the approved footprint, no-go areas, weather and flow forecast, fish passage, water quality controls and stop-work actions.
  • Keep machinery, fuels, oils, spoil and concrete materials outside the channel and above the one-in-100-year flood level where required by the environmental management plan.
  • Inspect sediment fencing, bunds, bank protection, diversion structures and spill controls before work and after rainfall or flow events.
  • Monitor turbidity, electrical conductivity, pH, dissolved oxygen, temperature, rainfall, visible oil and litter at the approved upstream and downstream sites.
  • Stop or secure floodplain works when rainfall or river levels could inundate the site, mobilise sediment or obstruct natural flow.
  • Prevent artificial lighting from shining into the waterway at night, particularly during periods when larvae or fish may be moving.

During habitat disturbance: 2. Coordinate the fauna spotter catcher and machinery

  • Use a suitably authorised aquatic fauna specialist or fisheries operator for fish capture, handling, exclusion, rescue and release.
  • Require the spotter catcher to inspect the work area and any isolated water before machinery enters, and to maintain communication with the operator by radio or agreed hand signals.
  • Move plant slowly near banks and water, keep the approved exclusion zones intact and stop immediately when the spotter catcher identifies fish, a blocked passage, sediment release or an unapproved impact.
  • Do not chase, net or handle Australian Grayling unless the person has the required authority, training and equipment.
  • Keep any captured fish in clean, aerated water for the shortest possible time and release them into suitable nearby retained habitat or the approved release location.

During habitat disturbance: 3. Respond to animals and aquatic habitat incidents

  • If an Australian Grayling is found, stop the relevant activity, keep the fish in water, photograph it only if this will not increase handling stress, and notify the environmental manager and authorised aquatic specialist.
  • Do not relocate fish across a barrier, into unsuitable water, into a different catchment or without approval from the relevant authority.
  • Refer injured fish promptly to a veterinarian, fisheries authority or authorised wildlife carer, following the approved incident procedure.
  • Stop work for any unapproved fish mortality, fish stranding, loss of passage, major spill, visible sediment plume, fish distress, bank collapse or failure of a temporary diversion.
  • Record the species, number, life stage or size, location, time, condition, activity underway, weather and flow, people involved, photographs, response and release or treatment outcome.
  • Report notifiable incidents to the approval authority, fisheries agency and other parties listed in the project management plan.

After habitat disturbance: 1. Complete post-work checks

The end of construction does not end the risk. Check that passage, water quality, banks and riparian cover have been restored before removing controls or closing the project environmental file.

  • Inspect the channel, banks, pools, riffles, tributaries, temporary crossings and downstream receiving waters for barriers, stranded fish, sediment deposits, erosion, scour, spills and loss of cover.
  • Remove temporary structures, bunds, access controls and materials that could obstruct fish movement or alter flow, unless an approved design requires them to remain.
  • Confirm that all disturbed floodplain and bank areas have been stabilised and that stormwater, road runoff and bridge drainage cannot discharge untreated pollutants to the waterway.
  • Continue water quality, rainfall and flow monitoring for the period specified in the approval and environmental management plan.
  • If a major flood, spill, landslip, fish kill or other incident occurs, implement an authority-approved Australian Grayling monitoring programme.

After habitat disturbance: 2. Monitor and report outcomes

  • Monitor rehabilitated areas for at least two years where floodplain or riparian rehabilitation has been undertaken, including revegetation, weeds, erosion and bank stability.
  • Use pre-work baseline data and upstream reference sites to compare turbidity, temperature, dissolved oxygen, pH and conductivity after construction.
  • Undertake follow-up fish surveys where required by approval conditions, where habitat or passage was altered, or where an incident may have affected the species.
  • Report captures, mortalities, fish passage problems, water quality exceedances, rehabilitation results and corrective actions to the relevant authorities and state biodiversity database.
  • Retain survey data, photographs, permits, inspection records, incident reports and monitoring results with the project environmental records.

After habitat disturbance: 3. Maintain controls and address residual impacts

  • Keep erosion, sediment, spill, weed and access controls in place until the site is stable and the environmental manager authorises removal.
  • Repair failed bank protection, revegetation, fish passage or drainage controls promptly and record the corrective action.
  • Assess any unavoidable residual impact under the EPBC Act and relevant state requirements, including whether an approved offset or other conservation measure is required.
  • Do not treat a short-term absence of detected fish as evidence that the habitat is no longer used.

Rehabilitation actions: 1. Restore channel, banks and riparian habitat

Rehabilitation should restore a connected river system rather than only replanting the construction footprint. Prioritise flow, fish passage, water quality, bank stability, shading and links between freshwater and estuarine habitat.

  • Reinstate the natural channel profile, pool and riffle sequence, stable banks and unobstructed low-flow and high-flow paths where works have altered them.
  • Replant locally appropriate native riparian species suited to the catchment to provide shade, bank stability, leaf litter and cover, using the approved regional revegetation schedule rather than introducing non-local species.
  • Retain or reinstate suitable instream cover, including naturally occurring snags and stable woody material, only where this will not create a fish passage or flood risk.
  • Prevent sediment delivery by stabilising bare ground, controlling runoff, repairing erosion and maintaining ground cover during establishment.
  • Remove weeds and prevent weed spread from machinery, fill and disturbed banks.

Rehabilitation actions: 2. Restore connectivity and water quality

  • Remove temporary barriers and modify permanent crossings, weirs or other structures where approved works can improve upstream and downstream movement.
  • Maintain connection between freshwater reaches, lower river reaches, estuaries and the sea because Australian Grayling requires movement between these habitats during its life cycle.
  • Design wetlands, drains and floodplain works to avoid trapping fish, cutting off migration routes or sending untreated sediment and pollutants to the river.
  • Use environmental flow advice and local hydrological information to retain flow cues for migration and spawning.
  • Control introduced fish and pathogens in accordance with state biosecurity and fisheries programmes, without releasing or moving fish between catchments.

Rehabilitation actions: 3. Monitor rehabilitation success

  • Monitor rehabilitation for a minimum of two years where required, checking native plant establishment, weed cover, bank stability, erosion, shading, water quality and fish passage.
  • Set success measures before works begin, including stable banks, no ongoing sediment discharge, functioning passage at all flows assessed by the project and establishment of the approved native riparian cover.
  • Repeat fish surveys using approved methods where the project affected habitat, flow, passage or water quality, and compare results with baseline and reference sites.
  • Investigate poor recruitment, fish mortality, persistent barriers, low flows or degraded water quality with the relevant fisheries and waterway authorities.
  • Use monitoring results to replace failed plantings, repair erosion, remove obstructions and revise controls rather than closing the rehabilitation action solely because construction is complete.

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