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Murray Cod (Maccullochella peelii)

The Murray Cod is a large, long-lived freshwater fish of the Murray-Darling Basin, occurring in rivers, creeks, billabongs and impoundments with warm water and substantial woody cover. It is listed as Vulnerable under the EPBC Act and Endangered in Victoria, so works that affect waterways, snags, riparian vegetation, water temperature, flow or fish passage may affect the species or its habitat.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

Victoria, Flora and Fauna Guarantee Act 1988: Endangered.

Breeding season

Timing varies with water temperature, flow and location. The table shows a typical pattern for the Murray-Darling Basin and should be adjusted for local hydrology and records.

Murray Cod surveys are generally preferred from March to August. The supplied survey guideline advises avoiding September to December to reduce interference with breeding.

  • Movement and spawning preparation: Adults may move upstream before spawning as water levels rise and temperatures increase. Migration and spawning are generally described from spring into early summer.
  • Breeding: Spawning is usually October to December, with reports of mid-October to mid-December timing. Eggs are deposited on snags, rocks or firm clay and guarded by males.
  • Young: Eggs hatch after about 5 to 13 days. Larvae drift downstream, then settle into protected woody habitat. High water levels and spring floods can improve larval and juvenile survival.
  • Adult and juvenile sheltering: Adults and juveniles use snags, deep holes, sluggish water, aquatic vegetation, undercut banks and other cover throughout the year.
  • Highest clearing risk: September to December has the highest risk because adults may be moving to spawning habitat, eggs and larvae are present, and breeding habitat and downstream drift pathways are sensitive to disturbance.

Identification

Murray Cod is a large freshwater percichthyid associated with cover in rivers and wetlands. Identification during field work should be undertaken by an experienced freshwater fish ecologist, particularly where Trout Cod or stocked and translocated fish may occur.

This is one of Australia's largest freshwater fish. It occurs in clear rocky streams, slow-flowing turbid rivers, billabongs and impoundments. Adults and juveniles are typically associated with submerged timber, deep holes, undercut banks, boulders, overhanging vegetation and other cover.

Maximum recorded size: Approximately 1.8 m long and 113.5 kg

Typical habitat depth: Generally up to 5 m deep

Typical position: Sheltered water near timber, rock or overhanging banks

Identification: Distinguishing from similar fish

Murray Cod can occur in the same broad river system as Trout Cod and other large native perches. The supplied sources do not provide a diagnostic field description or a complete character key, and larvae can present identification difficulties. Obtain clear photographs or retain specimens under the relevant permit and have uncertain fish identified by a qualified ichthyologist.

  • Do not rely on size or habitat alone to separate Murray Cod from Trout Cod or other native perches.
  • Treat larvae and small juveniles as requiring expert identification because identification complications are documented for early life stages.
  • Record the waterway, habitat, photographs and, where lawful, genetic material when species identity is uncertain.

Identification: Field signs

Fish themselves are the principal field evidence. The species does not produce terrestrial tracks, scats, nests, sloughs or detectable calls. Eggs may be deposited on snags, rocks or firm clay, and males guard the eggs, but eggs and larvae should not be disturbed during works or surveys.

  • Look for large fish holding beside or within 1 m of submerged woody debris.
  • Search sheltered pools, undercut banks, deep water and timber during daylight visual surveys where water clarity allows.
  • Use non-destructive survey methods and minimise handling, especially during the breeding period.

Distribution: National range

Murray Cod is naturally distributed through the warmer waterways of the Murray-Darling Basin. The distribution is broad but populations are patchy and fragmented, with many waterways affected by habitat loss, barriers, altered flows and cold water releases.

The natural range includes waterways in the Australian Capital Territory, New South Wales, South Australia and Victoria. The species also occurs in southern Queensland west of the Great Dividing Range, within the Murray-Darling drainage. The upper reaches of the Murray and Murrumbidgee Rivers may be too cold to provide suitable habitat.

Natural drainage: Murray-Darling Basin

States and territories identified in the sources: ACT, NSW, Qld, SA and Vic

Potential waterway length assessed in the basin: Approximately 13,245 km

  • Assess rivers, creeks, billabongs, wetlands and impoundments within the Murray-Darling Basin where warm freshwater habitat and woody cover are present.
  • Include downstream areas that may be affected by changes to flow, water temperature, sediment or fish passage.

Distribution: Populations and strongholds

The species is not represented by a single continuous, uniformly occupied population. Surveys have described populations as fragmented and patchy, with low abundance in many areas. Translocated populations occur in some NSW and Victorian impoundments and waterways, but many have depended on hatchery releases and few are known to have become self-sustaining.

Physical barriers identified in the basin: More than 3,600 dams, weirs, levees, causeways, culverts and road crossings

Population estimate: The number of mature individuals is unknown

Historical decline indicator: Commercial catch weights in NSW and SA declined from about 140 tonnes to about 20 tonnes per year over approximately seven to eight years in the late 1950s and early 1960s

Conservative decline estimate used for listing: About 30% over the previous 50 years

  • Treat apparently isolated reaches as potentially important subpopulations rather than assuming that nearby waterways provide equivalent habitat.
  • Check state databases and local records because stocked or translocated fish may occur outside the natural distribution.

Distribution: Distribution and development assessment

A site may support Murray Cod even where fish are not observed during a short survey. The species is territorial and sedentary for much of the year, while spawning adults may move upstream and larvae drift downstream. Assess both the occupied reach and connected upstream and downstream habitat.

  • Map all snags, deep pools, undercut banks, riparian cover, barriers and connected waterways within and downstream of the project area.
  • Consider stocked populations and records from anglers, agencies and local fish groups when determining whether the species may occur.
  • Do not interpret an absence from a single survey as evidence that suitable habitat is unoccupied.

Habitat: Waterways and climate

Murray Cod uses warm freshwater habitats ranging from clear rocky streams to slow-flowing turbid rivers, billabongs and impoundments. Habitat quality is strongly linked to instream woody debris, shelter, water temperature, flow and connectivity.

Adults and juveniles occur in rivers and creeks, including deep pools and sluggish reaches, as well as billabongs and some impoundments. The species is associated with warm water, and cold upper catchments or reaches affected by cold releases may be unsuitable or suboptimal.

Spawning temperature information: Spawning is associated with water temperatures of approximately 16 to 21 degrees Celsius in the EPBC advice, and about 20 degrees Celsius in the Queensland habitat summary

Cold water pollution impact: Water downstream of dams may be lowered by up to 15 degrees Celsius, with effects commonly extending 100 to 150 km and sometimes 200 to 400 km

  • Assess water temperature and seasonal flow patterns, not just the presence of open water.
  • Include connected billabongs, backwaters and floodplain habitats where project works may alter inundation or fish access.

Habitat: Structural habitat

Submerged woody debris, debris piles and bank-side vegetation provide shelter from high water velocities, feeding habitat, spawning surfaces and cover for young fish. Other important features include deep holes, boulders, undercut banks, overhanging vegetation, aquatic vegetation and firm clay or rock substrates.

Fish near snags: About 80% of fish in one radio-tracking study were within 1 m of a snag

Woody debris association: About 97% of fish had woody debris within a 12 m by 12 m surrounding grid in the same study

Juvenile association: About 94% of first-year fish were observed associated with woody debris

  • Retain snags and large woody debris in the channel and along the bank unless removal is required for an immediate safety reason and has been assessed.
  • Protect overhanging and riparian vegetation that shades banks and contributes cover and prey habitat.
  • Avoid infilling, sedimentation or bank erosion that reduces the depth of pools or covers spawning substrates.

Habitat: Connectivity and flow

Murray Cod may move upstream before spawning and use connected habitats throughout the river system. Dams, weirs, causeways, floodgates, culverts and road crossings can restrict movement, alter flow and increase mortality of larvae and juveniles.

Recorded upstream movement: Up to 240 km in an unregulated Ovens River

Regulated river movement: Fish moved less often and shorter distances in a highly regulated Murray River reach

  • Inspect proposed crossings for barriers to upstream and downstream fish movement.
  • Maintain fish passage during construction and after completion, including during low flows and changing water levels.
  • Manage sediment, turbidity, dewatering and discharge so that connected habitat is not degraded.

Foraging habitat: Diet

Murray Cod is a top-order aquatic predator. Adults feed in and around freshwater channels, pools, snags, aquatic vegetation and riparian cover, while larvae and juveniles use flowing channels and sheltered habitat as they develop.

Adults feed on fish, frogs and invertebrates, and may occasionally take reptiles, birds and aquatic mammals. Larvae feed on crustaceans, insects and zooplankton.

Adult prey: Fish, frogs, invertebrates and occasionally reptiles, birds and aquatic mammals

Larval prey: Crustaceans, insects and zooplankton

  • Protect snags, aquatic vegetation, undercut banks and riparian vegetation that support prey and provide ambush cover.
  • Prevent sediment, pollution and altered temperature from reducing aquatic invertebrate and small fish prey.

Foraging habitat: Foraging locations and behaviour

Adults prefer slow-flowing or sluggish water, deeper holes and sheltered areas around timber, rocks, undercut banks and overhanging vegetation. The species is territorial and generally sedentary, although it can move long distances before spawning.

Typical depth range: Generally found in water up to 5 m deep

Foraging range: A specific foraging range is not given in the supplied documents

  • Survey likely foraging habitat around snags, deep pools, bank cover and aquatic vegetation rather than only in open mid-channel water.
  • Retain habitat complexity on both banks and within the channel where works affect a waterway.
  • Consider upstream and downstream prey habitat when assessing temporary flow diversion, dewatering or construction discharge.

Breeding habitat: Breeding biology

Murray Cod breeds annually in spring to early summer. Breeding depends on warm water, suitable hard or woody spawning surfaces, upstream access, and flows that support larval drift and food production.

Adults commonly migrate upstream before spawning as water levels and temperatures rise. Adhesive eggs are laid on snags, rocks or firm clay. Males guard the eggs. Larvae hatch after several days and drift downstream before settling into protected habitat.

Breeding season: October to December, with spawning described as mid-October to mid-December

Spawning frequency: Annual

Egg and spawning substrate: Snags, rocks and firm clay; eggs are adhesive

Egg guarding: Males guard the eggs

Time to hatching: Approximately 5 to 13 days, depending on temperature

Age at maturity: Usually about 5 years, with reported variation from 3 to 6 years

Maturity size: Approximately 50 cm, with mature fish commonly weighing 2 to 4 kg

Lifespan: About 30 years in the Queensland summary; estimates of 75 to 114 years are reported for exceptionally old fish in the EPBC advice

Clutch or litter size: Not stated in the supplied documents

  • Avoid in-channel disturbance, dewatering, snag removal, noisy works and barriers during the breeding period.
  • Protect spawning surfaces and maintain upstream and downstream movement during spring and early summer.
  • Use larval drift sampling only under an approved survey design because larvae and their habitat can be disturbed.

Breeding habitat: Recruitment habitat

High water levels and spring floods can improve larval and juvenile survival by increasing food availability and water quality. Larvae drift downstream after hatching and juveniles settle in protected habitat, especially around woody debris.

Larval size at hatching: Approximately 6 to 9 mm

Recruitment pattern: Large recruitment events are strongly associated with spring flooding, although recruitment can occur in some low-flow years

Larval movement: Downstream drift after hatching

  • Maintain appropriate flow connectivity between spawning areas, larval drift pathways and downstream nursery habitat.
  • Prevent barriers, irrigation entrainment and hydroelectric diversion from intercepting drifting larvae.
  • Protect floodplain and billabong connections where they contribute to seasonal food production and recruitment.

Sheltering habitat: Adult and juvenile refuge

Shelter is a defining habitat requirement for Murray Cod. Fish use submerged timber, debris piles, deep holes, undercut banks, boulders, overhanging vegetation, aquatic vegetation and hollows in rock or wood.

Adults and juveniles rest and shelter among logs, sluggish water, deep holes, aquatic vegetation and other cover. Woody debris reduces exposure to fast water and predators and can also support prey.

Proximity to snags: About 80% of fish were recorded within 1 m of a snag

Woody debris surrounding habitat: About 97% of fish had woody debris within a 12 m by 12 m grid

Known refuge type: Hollows in rock or wood

  • Retain submerged and partly submerged trees, logs, root masses and debris piles within the channel.
  • Protect undercut banks, overhanging vegetation and deep pools from excavation, collapse and excessive sedimentation.
  • Do not assume that a snag is unoccupied because fish are not visible at the surface.

Sheltering habitat: Shelter for young fish

First-year fish are strongly associated with woody debris. Protected timber and low-velocity habitat provide cover while juveniles settle after the larval drift phase.

First-year fish associated with woody debris: About 94% in the cited study

  • Treat dense snag habitat and sheltered backwaters as potential nursery habitat.
  • Avoid rapid increases in flow velocity caused by desnagging, channelisation or temporary works.
  • Stage works to retain connected refuge habitat if part of a reach must be temporarily disturbed.

Threats: Clearing and channel works

The main threats are loss of woody habitat, altered flow and temperature, barriers to movement, fishing pressure and degradation of riparian and water quality. Construction can add direct risks through snag removal, dewatering, entrainment, sedimentation, bank disturbance and blocked fish passage.

Desnagging removes spawning surfaces, refuge and prey habitat and can increase flow velocity, channel erosion and sedimentation of deep holes. Clearing riparian vegetation removes bank cover, shade and prey habitat.

Historic snag removal: One snag boat removed approximately 176,400 to 235,200 snags over 49 years, and another is reported to have removed about 3 million snags

Murray River snag density example: About 3 snags per km was estimated in 1973 along a 330 km reach, compared with current site estimates of 27 to 140 snags per km

  • Do not remove snags, large woody debris or overhanging bank vegetation without a species-specific assessment and approval.
  • Fence and stabilise work areas to prevent bank collapse, stock access and sediment entry.
  • Retain deep pools, undercut banks and connected backwaters during channel and bank works.

Threats: Fragmentation, roads and infrastructure

More than 3,600 barriers in the Murray-Darling Basin restrict movement or alter habitat. Road crossings, culverts, causeways, weirs and floodgates can prevent access to shelter and spawning sites and increase larval or juvenile mortality.

Known barriers: More than 3,600 dams, weirs, levees, causeways, culverts and road crossings

Recorded movement distance: Up to 240 km upstream in an unregulated river

  • Design temporary and permanent crossings to maintain fish passage and avoid perched, blocked or high-velocity culverts.
  • Inspect and manage cofferdams, temporary bunds, pumps and bypass channels for entrapment and stranding.
  • Include downstream habitat and flow effects in assessments of dams, weirs and waterway crossings.

Threats: Hydrology and water temperature

Flow regulation has reduced the frequency of spring flooding, which is associated with strong recruitment. Cold water discharged from dams can reduce spawning success when temperatures would normally trigger migration and spawning.

Cold water reduction: Downstream water temperature may be reduced by up to 15 degrees Celsius

Typical cold water impact distance: About 100 to 150 km downstream, with effects sometimes extending 200 to 400 km

Affected NSW river length cited in the EPBC advice: Approximately 3,000 km

  • Avoid releases, diversion or construction discharges that create sudden temperature or flow changes during spring and early summer.
  • Maintain flow paths needed for upstream adult movement and downstream larval drift.
  • Manage erosion, turbidity, pollution and irrigation entrainment in connected waterways.

Threats: Fishing, introduced species and stocking

Commercial, recreational and illegal fishing can remove mature fish. Carp can damage aquatic vegetation and increase turbidity, while redfin perch may prey on larvae. Hatchery stocking may introduce disease or affect genetic integrity if broodstock and release practices are not controlled.

Fishing size relevant to mature fish: The legal minimum catch length in the range states is generally 50 cm, approximately the size at first maturity

Estimated NSW recreational catch cited in the EPBC advice: Approximately 144,000 fish annually, including about 45,100 kept and 98,900 returned, based on a limited sample

Stocking concern: High mortality before maturity, disease introduction and uncertain genetic effects are identified concerns

  • Apply the relevant fishing closures, handling requirements and permits during surveys and construction rescue operations.
  • Prevent the movement of fish, water, equipment and pathogens between catchments.
  • Do not release captured non-native fish back into the waterway where state rules prohibit it.
  • Use approved genetic and disease controls for any stocking or translocation program.

Survey methodology: 1. Boat or backpack electrofishing

Survey the waterway and connected habitats before works begin. Focus on warm freshwater rivers, creeks, pools, billabongs and impoundments with snags, large woody debris, overhanging banks, rocks, deep holes and slow flow.

Use boat-based electrofishing in suitable navigable water and backpack electrofishing in shallow water, following the Australian Code of Practice and operating equipment to minimise injury.

Target sheltered areas with submerged timber, rocks, overhanging banks and other cover, where Murray Cod are most likely to occur.

Electrofishing can be inefficient for Murray Cod in clear water during daylight because fish may hide, so combine it with other methods.

  • Use March to August as the preferred survey period.
  • Do not conduct routine surveys from September to December, when spawning occurs and disturbance may affect breeding.

Survey methodology: 2. Daytime snorkelling

Use daytime snorkelling where water clarity, depth, flow and safety allow visual detection.

Inspect snags, large woody debris, deep holes, undercut banks, rocks and overhanging vegetation.

Record the location, length and condition of important habitat features, not only fish observations.

Typical habitat association: About 80% of Murray Cod were reported within 1 metre of a snag.

  • Do not enter unsafe water or disturb unstable banks, snags or debris.
  • Use snorkelling with electrofishing or angling because visibility and fish behaviour can limit detection.

Survey methodology: 3. Angling and lure fishing

Use lure fishing or angling with barbless hooks to detect larger fish in pools and around submerged or partly submerged trees, logs and snags.

Murray Cod are generally more active at dawn, dusk and at night, making these periods suitable for lure fishing.

Release fish promptly and minimise handling, photographically documenting identification where needed.

  • Use spring and summer only where the work program permits, but avoid September to December because this overlaps the breeding period.
  • Treat a non-detection as inconclusive where fish may be present but unwilling to take a lure.

Survey methodology: 4. Larval drift sampling and other nets

Consider larval drift sampling where breeding or recruitment information is required and the method can be authorised and conducted without unacceptable disturbance.

Preserve larvae and arrange identification using an experienced fish taxonomist because larval identification can be difficult.

Fyke nets, gillnets, panel nets, light traps, gee traps and set-lines are specialist options for the large freshwater perch group and should be selected for the site and target life stage.

  • Check set-lines at regular intervals, such as every hour, to reduce stress and mortality.
  • Set gillnets for no longer than six hours and check them regularly.
  • Use gee or bait traps for small or juvenile fish only, and use light traps for larvae and juveniles.
  • Use non-destructive methods where possible, keep handling to a minimum and prevent injury to non-target fauna such as platypus.

Survey methodology: Minimum effort and reporting

  • Survey all waterway sections, pools, billabongs, wetlands and impoundments that could be affected directly or indirectly, including downstream areas.
  • Map snags, large woody debris, deep pools, overhanging banks, barriers, cold-water inputs, riparian cover and access points before sampling.
  • Record method, date, start and finish time, weather, water level, flow, turbidity, visibility, water temperature where measured, effort, equipment settings, habitat sampled and all detections or non-detections.
  • Use more than one method where habitat or visibility could reduce detection, rather than relying on a single negative result.
  • Have a suitably experienced fish ecologist or taxonomist confirm uncertain identifications, especially for larvae.
  • Submit confirmed records, negative survey information where requested, photographs and spatial data to the relevant state or territory wildlife database and the Australian Government threatened species systems where required.
  • Retain survey data with the project environmental records and provide it to the approval holder and relevant regulators.

Before habitat disturbance: Avoid and minimise habitat loss

Treat the waterway, its flow regime and its instream structure as fish habitat. Plan the project around the breeding period and avoid removing habitat features that support shelter, spawning, recruitment and movement.

Avoid direct disturbance to warm freshwater pools, billabongs, slow-flowing reaches, deep holes, undercut banks, overhanging vegetation and snag fields.

Retain large woody debris, logs, rocks, stable clay spawning surfaces, aquatic vegetation and riparian vegetation wherever practicable.

Maintain fish passage through the work area and do not create new barriers with crossings, bunds, cofferdams, culverts, spoil, fencing or machinery.

Protect downstream habitat from sediment, contaminants, altered flow, dewatering and sudden releases.

  • Map and mark all snags, log piles, deep pools, connected wetlands, fish passage routes and riparian cover before finalising the work footprint.
  • Use a site-specific aquatic habitat exclusion zone around retained features, based on the waterway assessment and project risk.
  • Do not remove or relocate snags unless the action has been assessed, authorised and supervised by the relevant aquatic ecologist.

Before habitat disturbance: Check approvals and timing

Confirm whether the action is likely to have a significant impact on a species listed as Vulnerable under the EPBC Act and obtain project approval or referral advice before work starts.

Check state and territory threatened species, fisheries, waterway, fish passage and animal handling requirements, including Victorian requirements because the species is listed as threatened there.

Schedule in-water disturbance outside September to December where practicable, because this is the identified spawning period.

If works cannot avoid the breeding period, document the justification and implement additional aquatic fauna controls in the fauna management plan.

  • Nominate the person responsible for EPBC Act compliance, state approvals, fish rescue and incident notification.
  • Include conditions from approvals, permits and the fauna management plan in the site induction and daily pre-start.

Before habitat disturbance: Prepare the site and work method

Complete a pre-clearance aquatic habitat survey before machinery enters the waterway or removes riparian cover.

Mark no-go areas, retained snags, banks, pools, wetlands, fish passage routes and pollution control zones with signage that operators can see from the work area.

Use exclusion fencing only where it will not block fish passage or isolate connected aquatic habitat.

Stage works so that undisturbed refuge habitat remains available while each work section is completed.

Prepare fish rescue, dewatering, water-quality, spill-response and unexpected-fauna procedures before construction.

  • Brief the fauna spotter catcher, aquatic ecologist, supervisor and machine operators on the mapped habitat and stop-work triggers.
  • Confirm the location of an authorised wildlife carer or veterinarian before works begin.
  • Keep machinery, fuels, concrete washout, spoil and chemicals away from the waterway and provide a controlled access point for any unavoidable entry.

During habitat disturbance: Daily controls and machinery coordination

Keep works inside the approved footprint and maintain water quality, flow and fish passage. A fauna spotter catcher must not replace an aquatic ecologist where fish rescue, dewatering or fish passage management is required.

Complete a daily pre-start inspection of water levels, flow, turbidity, barriers, exclusion zones, retained snags and pollution controls.

Keep plant on defined access routes and prevent machinery from driving over snags, banks, shallow pools or spawning substrates.

Use a spotter to control plant movement near retained habitat and stop the machine before contact with a marked snag, bank, pool or aquatic refuge.

Do not stockpile spoil, vegetation or debris in the channel, on banks or where material can enter the water.

  • Stop work during a spill, uncontrolled sediment release, fish stranding, unexpected dewatering, barrier failure or loss of fish passage.
  • Stop work if a Murray Cod or other protected aquatic fauna is found in the active work area until the authorised aquatic fauna handler assesses the situation.
  • Maintain erosion, sediment, turbidity and flow controls for the full duration of in-water works, including during rainfall and pump changes.

During habitat disturbance: Fish rescue and handling

Only personnel authorised under the relevant approval or permit should capture, handle, identify or relocate Murray Cod.

Minimise capture, air exposure, handling time and transport, and use clean equipment and water conditions appropriate to the fish.

Relocate a healthy fish only under the approved procedure, to nearby suitable retained habitat with appropriate depth, cover, water quality and connectivity.

Do not release fish into isolated pools, unsuitable water temperature, altered flow, another catchment or a location that could spread disease or compromise genetic integrity.

  • Have a qualified aquatic ecologist direct rescue during dewatering, isolation of pools, culvert works or barrier installation.
  • Place injured or stressed fish under the approved rescue protocol and obtain veterinary or wildlife rehabilitation advice promptly.
  • Do not use unapproved stocking or translocation as a substitute for rescue or habitat protection.

During habitat disturbance: Habitat features, incidents and records

Retain snags, logs, rocks, overhanging banks and aquatic vegetation in place unless their removal is specifically approved.

If a snag or log must be moved, have an aquatic ecologist assess whether it is spawning, shelter or passage habitat and record its original and final location.

Keep water connected and oxygenated during dewatering, and inspect isolated pools, pump intakes, culverts and downstream edges for stranded fish.

Record every detection, rescue, injury, death, relocation, barrier breach, water-quality incident and stop-work event.

  • Photograph and map any Murray Cod, occupied habitat, damaged snag, fish passage obstruction or pollution event.
  • Record date, time, location, life stage or size class, condition, method of capture, handler, destination and outcome for each handled fish.
  • Notify the project supervisor and the relevant regulator or approval contact when required by the approval, permit or incident procedure.

After habitat disturbance: Post-clearance inspection

Do not close out aquatic works when machinery leaves the site. Confirm that fish habitat, water quality, connectivity and site controls have been restored and that any approval conditions are met.

Inspect the full work area and downstream reach after clearance, dewatering, bank works or installation of crossings.

Check for stranded fish, isolated pools, damaged snags, blocked passage, eroded banks, sediment deposition, turbid discharges, rubbish and contaminated water.

Remove temporary barriers, pumps, hoses, spoil and debris that could obstruct fish passage once the authorised works are complete.

Confirm that retained pools, snags, woody debris, undercut banks, riparian vegetation and connected wetlands remain functional.

  • Repeat the inspection after the first substantial rainfall or flow event and after any failure of erosion or sediment controls.
  • Keep exclusion fencing and pollution controls in place until the site is stable and the environmental representative authorises their removal.

After habitat disturbance: Monitoring and reporting

Monitor water quality, flow, fish passage, bank stability and retained habitat for the period specified in the approval or fauna management plan.

Undertake follow-up fish surveys where works removed habitat, altered flow, affected connectivity or caused a fish rescue event.

Report survey results, incidents, mortalities, relocations, rehabilitation actions and unresolved risks to the approval holder and relevant regulators.

Submit confirmed species records and spatial data to the relevant state or territory wildlife database.

  • Compare post-work habitat condition with the pre-work map and photographs.
  • Document any remaining impact and implement additional habitat protection, restoration or approved offset actions where required.

Rehabilitation actions: Restore instream and riparian habitat

Rehabilitation should restore the physical features and flow conditions that Murray Cod use for shelter, spawning, feeding and movement. Design the works with an aquatic ecologist and maintain them until they are stable and functioning.

Reinstate appropriately placed large woody debris, logs, rocks and stable bank cover where these features were removed or damaged and where the approved design allows it.

Restore overhanging and riparian vegetation with locally appropriate native species suited to the waterway, bank and floodplain conditions.

Reform eroded banks and protect them with living vegetation and suitable natural materials rather than creating smooth, structureless channels.

Restore slow-flowing pools, deep holes and connected refuge habitat where these were altered by the project.

  • Do not place logs or rocks where they create a flood hazard, scour risk, navigation hazard or an unauthorised barrier to fish movement.
  • Use local aquatic and riparian advice to select plant species because the supplied documents do not specify a species list for every project location.

Rehabilitation actions: Restore flow, passage and water quality

Remove or modify temporary barriers and design permanent crossings, culverts, weirs and causeways to maintain fish passage under the approved design.

Avoid cold-water discharges, sudden flow changes, contaminated runoff, excessive sediment and altered floodplain connections.

Control weeds and prevent introduced fish impacts where these are identified in the project risk assessment.

Maintain clean machinery and biosecurity controls between waterways to reduce disease and introduced-species risks.

  • Inspect restored reaches for passage, water depth, flow, turbidity, bank stability and fish access during low and high flow conditions where practicable.
  • Coordinate flow rehabilitation with the relevant waterway manager because recruitment is associated with elevated water levels and high larval survival when a significant rise coincides with breeding.

Rehabilitation actions: Measure success and maintain the site

Set success measures for survival of planted riparian vegetation, stability of restored banks, persistence of snags and pools, unobstructed fish passage, water quality and Murray Cod use of the restored reach.

Inspect restored habitat regularly and replace failed plantings, repair erosion, remove weeds and correct any new obstruction or sediment accumulation.

Use follow-up electrofishing, daytime snorkelling, barbless angling or larval drift sampling where monitoring is approved and needed to assess fish response.

Report monitoring outcomes and adapt maintenance where restored habitat is not providing cover, spawning surfaces, food access or movement routes.

Spawning period: Generally mid-October to mid-December, with the broader survey guidance advising avoidance of September to December.

Key habitat association: About 80% of fish were reported within 1 metre of a snag.

  • Continue monitoring for the period required by the approval, recovery plan, offset plan or fauna management plan.
  • Do not claim rehabilitation success from a single fish detection or non-detection; assess habitat condition, connectivity and water quality alongside survey results.

Sources