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Freshwater Catfish (Tandanus tandanus)

Freshwater catfish (Tandanus tandanus) is a large, bottom-dwelling native fish of sluggish rivers, creeks, lagoons, billabongs and lakes across eastern and south-eastern Australia. It is sedentary, threatened in parts of its range, and sensitive to drying, altered flow patterns, loss of aquatic vegetation, siltation and water diversion, including entrainment of drifting larvae at pumps. On development sites, protect permanent and semi-permanent aquatic habitat, nests, aquatic vegetation and flow connections, particularly from spring to summer.

Conservation status

Victoria, Flora and Fauna Guarantee Act 1988: Endangered.

Breeding season

Timing varies between catchments and years, but breeding is associated with warm spring and summer water. The highest disturbance risk is usually from October to January, when adults may be nesting and larvae may be drifting towards downstream habitat and water diversions.

Months are coded January to December: 0, not typical; 1, occurs; 2, peak. Breeding timing can vary between catchments and years, so site-specific records and water temperature should be considered.

  • Breeding preparation and nesting: Spawning occurs in spring and summer. Males build and maintain circular nests in shallow areas, with recent Victorian evidence indicating spawning in November and December.
  • Eggs and hatchlings: Eggs are protected in the nest until hatching. The supplied documents do not give a precise incubation period.
  • Larval drift and early dispersal: Larval drift has been recorded from October to December, mainly overnight. Larvae were estimated at about 10 to more than 13 days old when drifting from the nest.
  • Juvenile settlement and local occupancy: Young fish were recorded in mid-February at Tahbilk Lagoon after spawning in November and December. Adults are largely sedentary and most individuals move less than 5 km.
  • Highest clearing risk: Clearing, bed disturbance, dewatering, rapid water-level changes and pumping are most likely to harm the species from October to January because nesting, hatching and larval drift overlap this period.

Identification

Freshwater catfish is a large, robust, bottom-dwelling catfish with a distinctive eel-like tail and barbels around the mouth. Live identification should be confirmed by an appropriately qualified aquatic fauna specialist because several native catfish species occur in Australian inland waterways.

The species belongs to the family Plotosidae and is also called eel-tailed catfish. It may occur in clear or turbid water over mud, gravel or rock, but generally prefers sluggish or still water. Adults can reach 900 mm and 6.8 kg, although fish over 2 kg are uncommon.

Scientific name: Tandanus tandanus

Family: Plotosidae

Body size: Up to 900 mm

Maximum recorded weight in the source: 6.8 kg

Identification: Distinguishing features

The eel-like tail, bottom-dwelling habit and catfish form are useful field characters. The species feeds, breeds and shelters near the substrate. Identification should also consider the local fish assemblage and regional records, because the taxonomic status of eastern and western populations has been under investigation.

  • Record the body shape, tail form, barbels, colour, size and substrate when photographing or handling a fish.
  • Use a recognised native fish identification key or obtain confirmation from a fisheries ecologist where the record may affect project approvals.

Identification: Field signs and sex differences

The most useful breeding sign is a circular nest in shallow water, commonly made from stones. Males maintain nests by fanning away sediment and defending them from predators until the eggs hatch. Sexes are not reliably separated by the field information in the supplied documents.

  • Inspect shallow margins, stony patches and other suitable substrate for circular nests before disturbing the bed or changing water levels.
  • Treat an occupied or recently maintained nest as a breeding site and refer the observation to the project aquatic ecologist.

Distribution: National range

Freshwater catfish occurs in inland eastern Australia and in some coastal river systems. The supplied sources identify populations in Queensland, New South Wales, Victoria and South Australia, with marked declines across the Murray and Darling drainage and stronger remaining populations in parts of northern and central inland New South Wales and the Border Rivers.

The western population was historically widespread through the Murray Darling River system in New South Wales, Queensland, Victoria and South Australia, except in the cooler southern tributaries. The species also occurs in freshwater areas, including tidal reaches of coastal rivers from the Shoalhaven River to the Tweed River in New South Wales, although some coastal populations may have resulted from translocation and their origin is uncertain.

  • In Queensland, records include the Border Rivers and southern Queensland waters.
  • In New South Wales, records include the Murray, Darling, Murrumbidgee, Lachlan, Macquarie, Castlereagh, Namoi, Gwydir and Border Rivers catchments, as well as some coastal rivers.
  • In Victoria, records include Tahbilk Lagoon near Nagambie, the Wimmera River and Cardross Lakes.
  • In South Australia, the species is protected and occurs in the lower Murray region.

Distribution: Strongholds and subpopulations

Moderate remnant populations are reported in the Macquarie catchment upstream of Warren, the Castlereagh catchment upstream of Mendooran, the Namoi catchment upstream of Wee Waa, the Gwydir catchment upstream of Moree and the Border Rivers catchment upstream of Goondiwindi. In Victoria, Tahbilk Lagoon is described as one of the few locations with a relatively abundant population.

  • The Border Rivers includes a candidate population for expansion of the species' core range, with freshwater catfish recorded at Bonshaw in the Dumaresq River.
  • The Yanco Creek system, particularly Colombo Creek, supports freshwater catfish records.
  • The Murrumbidgee Valley source identifies freshwater catfish in the Yanco Creek system and the Lowbidgee and Murrumbidgee region tables record the species.

Distribution: Trend and conservation status

The species has undergone a significant decline in abundance and distribution across the southern range and in riverine habitats of the Murray Darling Basin. The supplied documents describe an endangered population in New South Wales and threatened or endangered status in Victoria, while the user supplied project listing identifies Victoria as Endangered and the species as not listed under the EPBC Act.

EPBC Act: Not listed, according to the supplied project listing.

Victoria: Endangered, according to the supplied project listing.

New South Wales: Endangered population in the Murray Darling Basin.

South Australia: Protected.

Population trend: Significant decline in abundance and geographic distribution across much of the Murray Darling Basin.

Habitat: Waterways and wetlands

Freshwater catfish uses freshwater habitats ranging from flowing upland streams to lowland wetlands and lakes, but generally prefers sluggish or still water. Habitat suitability depends on water remaining present, aquatic vegetation, low to moderate flow, suitable bottom substrate and access to refuges such as lagoons, billabongs and backwaters.

Typical habitats include rivers, creeks, lakes, billabongs and lagoons. The species can live in clear or turbid water and over mud, gravel or rock, but is generally rare in natural riverine habitats where populations have declined. It prefers slow-flowing or still water and does not undertake regular long-distance migration.

  • Retain permanent and semi-permanent pools, backwaters, lagoons, billabongs and low-flow channel habitat.
  • Avoid allowing occupied habitat to completely dry, particularly during dry conditions.
  • Maintain within-channel low-flow conditions and suitable slow-flowing warm water through spring and summer.

Habitat: Habitat structure

Aquatic vegetation is an important habitat feature. In the Border Rivers, dense aquatic macrophyte beds in the Dumaresq River support freshwater catfish and other native fish. Suitable bottom habitat includes mud, gravel and rock, and shallow stony areas may support nests.

  • Protect aquatic macrophyte beds, shallow margins, woody habitat and varied channel features from clearing, dredging, trampling and smothering.
  • Avoid works that increase fine sediment deposition over gravel, rock or nest sites.
  • Retain connections between main channels, billabongs, lagoons and low-level wetlands where they support fish habitat.

Habitat: Climate and elevation

The supplied documents do not provide a defined elevation limit. Records span upland streams and lowland wetlands, while breeding is associated with warm water in spring and summer. Cold-water discharge from the base of large dams and high-level weirs is identified as a threat because it may remove temperature cues for spawning.

Elevation limit: Not specified in the supplied documents.

Breeding water temperature: Approximately 20 to 24°C.

Foraging habitat: Diet and feeding areas

Freshwater catfish is a benthic carnivore that feeds close to the bottom. It uses rivers, creeks, lagoons, billabongs and lakes with suitable substrate and slow or still water.

The diet includes crustaceans, mainly yabbies and shrimp, molluscs, aquatic insects and small fish. Feeding occurs near the bottom over mud, gravel or rock, including in sluggish or still water.

Feeding mode: Benthic and carnivorous.

Main recorded prey: Yabbies, shrimp, molluscs, aquatic insects and small fish.

Foraging range: A specific foraging range is not provided. Most individuals move less than 5 km, indicating that feeding areas may be used locally.

  • Inspect shallow margins, pools, backwaters, lagoon edges and vegetated areas as potential feeding habitat before works.
  • Retain benthic substrate, aquatic vegetation and water depth needed to support invertebrate and small fish prey.
  • Prevent sediment, chemical pollution and dewatering from reducing benthic food resources.

Breeding habitat: Breeding biology

Freshwater catfish breeds in warm, shallow habitat with stable water conditions and suitable nest substrate. Nesting adults and newly dispersed larvae can be affected by rapid water-level changes, altered flow, floods and unscreened water diversions.

Males construct circular nests in shallow areas, commonly using stones. The male maintains the nest by fanning away sediment and chasing predators, and protects the eggs until hatching. Larvae leave the nest at about 10 to 13 days after hatching and may drift downstream, mostly at night, before settling.

Breeding season: Spring and summer, broadly October to March.

Likely peak spawning period: November to December at Tahbilk Lagoon, based on larvae 10 to 15 days old in late November and young fish in mid-February.

Spawning temperature: About 20 to 24°C. Larval drift in the Macquarie River was recorded at 20.7 to 26.5°C, with a median of 24.6°C.

Nest: Circular, shallow-water nest, commonly made from stones.

Clutch size: Not specified in the supplied documents.

Incubation period: Not specified. Larvae were approximately 10 to 13 days old when observed drifting after leaving the nest.

Age at maturity: About 3 to 5 years.

Lifespan: Not specified in the supplied documents.

  • Avoid rapid fluctuations in water level during the breeding period.
  • Do not disturb shallow stony substrate, occupied nests or nearby aquatic vegetation.
  • Screen pumps and diversions or use other fish protection measures where larval drift may reach an intake.

Breeding habitat: Larval habitat and dispersal

Larvae have been recorded in the main river channel and adjoining irrigation channels. In a Macquarie River study, larvae were captured only in drift nets and not in light traps set in still-water edge habitat. Ninety six per cent of larvae in the diel sub-study were captured overnight, indicating that night-time flow paths and diversion intakes may present a particular risk.

Larval size recorded in river drift nets: 9.58 to 23.84 mm standard length.

Estimated larval age when drifting: About 10 to more than 13 days old.

Diel pattern: Ninety six per cent of 49 larvae in the diel sub-study were captured overnight.

  • Maintain a connected low-flow channel during the breeding and larval period.
  • Assess pumps, offtakes, regulators and irrigation channels for larval entrainment risk from October to December.
  • Use fish-friendly screens, bypasses, adjusted pumping times or other approved measures where a diversion can intercept drifting larvae.

Sheltering habitat: Refuge habitat

Freshwater catfish shelters and spends much of its life in the same local area. Suitable refuges include slow-flowing pools, still water, lagoons, billabongs, backwaters and habitats with aquatic vegetation and varied substrate.

The species is non-migratory and most individuals move less than 5 km. It uses rivers, creeks, lakes, billabongs and lagoons, with a preference for sluggish or still water. In dry periods, connected pools and other water bodies that do not completely dry are important refuges.

Typical movement: Most individuals move less than 5 km.

Specific refuge dimensions: Not specified in the supplied documents.

  • Protect deep or persistent pools, off-channel lagoons, billabongs, backwaters and low-flow reaches from infilling, isolation and dewatering.
  • Maintain aquatic vegetation and substrate diversity around refuges.
  • Avoid blocking or severing connections between refuge pools and the main channel where fish need access during changing flows.

Sheltering habitat: Nest and bottom habitat

Adults live, feed and breed near the bottom. Circular stone nests occur in shallow areas and are maintained by the male until eggs hatch. The species can use mud, gravel and rock substrates, but siltation can remove spawning sites and degrade bottom habitat.

  • Keep machinery, temporary crossings, sediment ponds and spoil away from shallow stony margins and the bed of occupied waterways.
  • Search for circular nests before bed disturbance, water-level changes or installation of in-stream structures.
  • Use sediment controls that prevent fine material from covering gravel, rock and aquatic vegetation.

Threats: Hydrology and habitat loss

The main risks are loss or drying of aquatic habitat, altered flow and flooding patterns, siltation, loss of aquatic vegetation, cold-water releases, introduced species, pollution and interception of drifting larvae at water infrastructure. Construction can add to these pressures through dewatering, bed disturbance, sediment release, bank works and rapid changes in water level.

Freshwater catfish is at risk under low-flow and cease-to-flow conditions because it is sedentary and does not readily respond to changing water levels. River regulation, loss of lagoons and billabongs, altered flooding regimes and rapid water-level fluctuations can reduce habitat and spawning success.

  • Do not allow known or potentially occupied habitat to completely dry during works or water management operations.
  • Maintain low-flow conditions and avoid rapid rises or falls in water level near nests.
  • Retain flow connections to wetlands, lagoons, billabongs and backwaters where they provide habitat or recruitment opportunities.
  • Assess temporary dams, cofferdams, diversions and culverts for loss of fish passage and refuge habitat.

Threats: Construction and clearing risks

Direct risks on development sites include clearing or filling aquatic habitat, disturbing the bed, removing aquatic vegetation, increasing turbidity and smothering substrate with silt. Roads, crossings, pipes, regulators and weirs can fragment habitat or alter local flow and fish passage.

  • Keep plant, access tracks, stockpiles and spoil out of waterways, shallow margins, lagoons and wetland depressions.
  • Use sediment and erosion controls before earthworks start and maintain them until exposed ground is stabilised.
  • Schedule in-stream disturbance outside the spring and summer breeding period where practicable, and inspect for nests before any unavoidable works.
  • Provide a qualified aquatic fauna spotter during fish rescue, dewatering and removal of temporary barriers.
  • Do not relocate or handle fish without the required approvals and an approved fish rescue method.

Threats: Pumps, diversions and predators

Larvae drift downstream after leaving the nest and can be entrained at unscreened pumps and water diversions. Introduced carp, chemical pollution, historical fishing, siltation, loss of aquatic plants and cold-water discharge are also identified threats.

Larval entrainment evidence: Larvae were recorded in irrigation channels, including 38 in one channel and 11 in another during the 2020 to 2021 study season.

Highest observed channel density: Up to one larva per 2 mL during sampling periods when larvae were present in an irrigation channel.

  • Fit or maintain fish protection screens, bypasses or fish-friendly diversion structures where pumps or offtakes can intercept larvae.
  • Review pumping schedules and locations during the October to December larval drift period, including overnight operation.
  • Prevent concrete washout, fuels, pesticides, sediment and other pollutants from entering fish habitat.
  • Control carp and other introduced species in accordance with the relevant state programme and approvals.

Threats: Fire, roads and disease

The supplied documents do not identify fire, roads or disease as specific primary threats for this species. These pressures can still affect aquatic habitat indirectly through erosion, sediment delivery, altered drainage, barriers and water-quality decline.

  • After fire or road works, inspect downstream pools, wetlands and crossings for sediment pulses, debris barriers and loss of water.
  • Prevent road runoff, drainage concentration and accidental chemical releases from reaching occupied waterways.
  • Report unusual fish deaths, lesions or disease signs to the relevant state fisheries authority and follow biosecurity procedures.

Survey methodology: 1. Targeted fish survey

Freshwater catfish are benthic, largely sedentary fish of slow flowing or still water, including rivers, creeks, lagoons, billabongs and farm dams. Surveys must cover both the aquatic habitat and infrastructure that can affect breeding, larval drift and refuge pools.

Use a suitably licensed freshwater fish ecologist to survey retained and potentially disturbed rivers, creeks, lagoons, billabongs, wetlands, farm dams and connected irrigation channels.

Use methods suited to site conditions and approvals, such as backpack or boat electrofishing, seine nets, fyke nets, bait traps or other approved fish sampling methods.

Survey shallow margins, slow flowing reaches, pools, backwaters, aquatic vegetation, woody debris and substrates of mud, gravel or rock, because the species is benthic and prefers sluggish or still water.

Record the survey area, waterbody type, connection to other waterways, water depth, flow, aquatic vegetation, woody debris, substrate, barriers, pumps, weirs and other water extraction points.

Typical adult movement: Most individuals move less than 5 km.

Preferred habitat: Slow flowing or still warm water, with aquatic vegetation and benthic habitat.

  • Obtain all required fisheries, animal ethics and land access approvals before capture or handling.
  • Use experienced freshwater fish personnel because the species may be confused with other catfish and survey methods can injure fish if poorly selected or operated.
  • Release captured fish at the point of capture unless an approved translocation or salvage plan specifies another nearby retained habitat.

Survey methodology: 2. Breeding and larval survey

Plan targeted breeding surveys from spring to summer, with particular attention to November and December, when spawning and hatching have been recorded and water temperatures are commonly about 20 to 24 degrees Celsius.

Inspect shallow areas for circular nests made from stones or other substrate, but do not stand on, disturb or remove nest material.

Use approved larval drift nets or equivalent methods operated by qualified fish ecologists where larval recruitment is relevant to the project.

Sample the flowing channel as well as slow water edges and connected irrigation channels, because larvae have been recorded in river currents and irrigation channels and may not be detected by still water light traps.

Larval drift period recorded: October to December, when water temperatures exceeded 21 degrees Celsius.

Larval size and estimated age: About 9.3 to 23.9 mm standard length and about 10 to more than 13 days old in river drift samples.

Recorded capture temperatures: 20.7 to 26.5 degrees Celsius.

  • Include overnight drift sampling where feasible, because 96 per cent of larvae in one diel study were captured overnight.
  • Treat larval surveys as time sensitive, with effort concentrated during the October to December spawning and early dispersal period.
  • Do not infer absence from a failed light trap survey, because no freshwater catfish larvae were captured in overnight light traps in the cited study.

Survey methodology: 3. Habitat and connectivity assessment

Map aquatic vegetation, woody debris, refuge pools, slow flowing reaches, lagoons, billabongs, wetlands, anabranches and off-channel habitats within and downstream of the work area.

Map weirs, regulators, culverts, pumps, irrigation offtakes, screens, diversion channels and other structures that may interrupt fish movement or entrain larvae.

Assess whether the project could cause drying, rapid water level changes, loss of aquatic plants, siltation, cold water discharge, reduced flow or disconnection from nearby habitat.

Survey both the proposed disturbance footprint and nearby retained habitat that could receive salvaged fish.

  • Record water temperature, flow condition, depth, substrate, aquatic vegetation and woody debris at each survey location.
  • Identify refuges that must remain wet during works, because habitats cannot be allowed to completely dry.

Survey methodology: Minimum effort and reporting

  • Use a qualified aquatic ecologist to set the survey method and effort for the waterbody, season, accessibility, expected disturbance and approval conditions, because the supplied documents do not prescribe a universal number of transects, trap nights or survey hours for this species.
  • Repeat surveys during the breeding and larval period where works could affect nests, spawning habitat, larval drift or water extraction.
  • Report all captures, nest observations, larvae, mortalities, injuries, habitat observations, flow conditions and infrastructure risks with coordinates, dates, methods and photographs.
  • Submit confirmed records and incident records to the relevant state wildlife, fisheries or biodiversity database, and provide records to the project approval authority where required.
  • Retain field sheets, permits, calibration records, photographs, chain of custody information and fauna handling records in the project environmental file.

Before habitat disturbance: Avoid and minimise

Plan the project around the species' dependence on slow flowing or still water, aquatic vegetation, stable breeding habitat and connected refuge pools. Treat pumps, diversions, weirs and rapid changes in water level as potential risks, especially from October to December.

  • Retain slow flowing reaches, pools, lagoons, billabongs, wetlands, aquatic vegetation, woody debris, shallow nest areas and mud, gravel or rock substrates.
  • Keep connected refuge pools wet and avoid works that cause a complete drying of the occupied habitat.
  • Retain longitudinal and lateral connectivity between the main channel, anabranches, billabongs, wetlands and off-channel habitat where practicable.
  • Avoid locating pumps, offtakes, temporary crossings, access tracks or discharge points in known catfish habitat or in the likely path of drifting larvae.
  • Avoid rapid fluctuations in water level during the spring and summer breeding period, because changing levels can cause nest abandonment.

Before habitat disturbance: Approvals and fauna planning

  • Check the current EPBC Act status and obtain specialist advice on whether referral is required, noting that the supplied profile identifies the species as not listed under the EPBC Act.
  • Check current state threatened species, fisheries, animal ethics, collection, handling, translocation and waterway work requirements before works begin.
  • Prepare a species specific fauna management plan covering survey, salvage, handling, release locations, injured animals, nest protection, water quality, pump operation, stop work triggers and reporting.
  • Nominate the authorised aquatic ecologist, fauna spotter catcher, site supervisor, wildlife carer and veterinary contact before mobilisation.
  • Consult the relevant state fisheries and wildlife agencies where the project may affect an endangered or threatened population.

Before habitat disturbance: Timing and site preparation

  • Schedule in channel disturbance outside the spring to summer breeding period where practicable, with particular care during October to December.
  • Stage works so that retained refuge pools, aquatic vegetation and connected slow water remain available throughout construction.
  • Complete the pre-clearance aquatic survey immediately before disturbance and repeat it after any major change in flow, water level or work footprint.
  • Mark nest areas, refuge pools, aquatic vegetation, woody debris, pumps, diversion points and no-go habitat on plans and on the ground or water surface.
  • Install exclusion fencing, silt controls and machinery access controls where they can protect the waterbody without blocking fish movement or stranding fish.
  • Prepare clean holding containers, aeration, water quality equipment, nets, measuring equipment and approved release locations before any salvage operation.

During habitat disturbance: Daily controls

Keep the aquatic habitat wet, connected and free from avoidable disturbance. The fauna spotter catcher must have authority to stop work and must work directly with the operator and aquatic ecologist.

  • Inspect refuge pools, flow paths, nest areas, aquatic vegetation, silt controls, pump intakes, screens, diversion channels and exclusion fencing before work each day.
  • Maintain low flow through occupied habitat and prevent complete drying, sudden drawdown, uncontrolled discharge and sudden changes in water level.
  • Keep fuel, concrete, sediment, wastewater, chemicals and spoil out of the waterway and stop work if water quality deteriorates or fish are distressed.
  • Use fish friendly pumps, screened intakes, bypasses or approved isolation and salvage procedures where water must be removed.
  • Control noise, vibration, vehicle access and bank disturbance near shallow nest habitat and retained aquatic vegetation.

During habitat disturbance: Fauna spotter catcher and machinery

  • The fauna spotter catcher must inspect the work area and waterbody before machinery enters and must remain able to see the active disturbance zone.
  • The machine operator must stop immediately when directed by the fauna spotter catcher, aquatic ecologist or site supervisor.
  • Use an aquatic ecologist or other authorised person for capture, identification, handling and release of fish, rather than relying on general construction personnel.
  • Move machinery progressively and only after the next work area has been checked for fish, nests, shallow refuge habitat and connected flow paths.
  • Keep machinery out of mapped refuge pools, aquatic vegetation and nest areas unless the approved method specifically requires entry.

During habitat disturbance: Animal finds, salvage and stop work

Primary breeding concern: Rapid water level changes can cause nest abandonment and reduce egg laying, fertilisation and protection.

Larval risk: Downstream drifting larvae can be entrained at unscreened pumps and water diversions.

  • Stop work immediately if a freshwater catfish, nest, concentrated fish mortality, stranded fish or unexpected occupied habitat is found in the disturbance area.
  • Do not touch, chase, lift or relocate the animal unless the person is authorised and the approved fauna management plan permits it.
  • If salvage is approved, keep handling brief, use clean wet equipment and suitable aerated water, and release fish into nearby retained habitat with similar flow, temperature, depth, substrate and cover.
  • Do not release fish across a barrier, into unsuitable fast water, into a drying area or into a location affected by construction discharge.
  • Send injured or distressed fish to the nominated aquatic wildlife rehabilitator or veterinarian and record the advice and outcome.
  • Escalate any nest disturbance, fish mortality, pump entrainment, barrier failure, loss of flow or water quality incident to the project environmental officer and relevant authority before restarting work.

During habitat disturbance: Records and incident reporting

  • Record the date, time, location, water conditions, work activity, species, number and life stage of every capture, nest, injury, mortality, relocation and stop work event.
  • Photograph fish, nests, habitat, pumps, screens, barriers and any incident where this can be done without further disturbance.
  • Record release coordinates, habitat condition, holding time, water quality observations, authorised personnel and any veterinary or wildlife carer advice.
  • Report incidents through the approval, fisheries and wildlife reporting pathways and update the fauna management plan if controls were ineffective.

After habitat disturbance: Post-clearance checks

Confirm that no fish, nests or refuge habitat remain at risk after each work stage. Continue controls until the waterway, banks and connected habitats are stable and the project environmental officer closes the inspection.

  • Inspect the full disturbance area, downstream reach, temporary pump locations, diversion channels and isolated pools for stranded fish, nests, dead fish, injured fish and blocked flow paths.
  • Check that refuge pools remain wet, water levels are stable, aquatic vegetation is not buried, and woody debris and suitable benthic substrate have not been unnecessarily removed.
  • Remove temporary barriers, hoses, screens and crossings only after confirming that fish will not be stranded or swept into unsafe infrastructure.
  • Repair erosion, sediment controls, bank damage, leaks and any obstruction that affects fish passage or refuge habitat.
  • Undertake a follow-up aquatic survey where the project caused dewatering, barrier installation, major flow change, water quality impact or direct fish mortality.

After habitat disturbance: Monitoring and reporting

  • Monitor retained habitat through the next suitable breeding season where works affected spawning habitat, aquatic vegetation, water levels or connectivity.
  • Where breeding habitat was affected, inspect for nests, larvae and young fish during spring and summer, with particular attention to November and December.
  • Monitor pump intakes, screens, bypasses and diversion channels during the larval drift period, especially at night when drift is more likely to be detected.
  • Compare post-work observations with pre-work records for flow, water depth, temperature, aquatic vegetation, woody debris, substrate, fish presence and connectivity.
  • Submit final survey, salvage, incident, monitoring and database records to the project approval authority and relevant state agency.

After habitat disturbance: Controls, offsets and residual impacts

  • Maintain exclusion fencing, no-go markers, fish screens, flow controls, water quality controls and access restrictions until the environmental officer confirms that they are no longer needed.
  • Assess residual loss of habitat, connectivity, spawning sites, refuge pools or recruitment after avoidance and rehabilitation measures are complete.
  • Apply any offset, compensatory habitat, conservation stocking or other approved action only where required by the relevant approval or agency direction.
  • Do not use stocking or translocation as a substitute for retaining occupied habitat and preventing construction impacts.

Rehabilitation actions: Aquatic habitat restoration

Rehabilitation must restore stable, connected aquatic habitat rather than only replanting the bank. Prioritise slow water, refuge pools, aquatic vegetation, suitable nest substrate, woody habitat and safe fish passage.

  • Reinstate slow flowing pools, backwaters, lagoons, billabongs or wetland connections where these were disturbed and where the approved design allows.
  • Maintain permanent or seasonal refuge water and design the site so low flow conditions do not completely dry occupied habitat.
  • Replant or allow recovery of native aquatic vegetation in shallow margins and other areas used for cover and breeding.
  • Reinstate a natural range of mud, gravel and rock substrates, including shallow stable areas suitable for circular nests.
  • Retain or replace appropriately placed large woody debris where it provides cover, benthic habitat or flow diversity, without creating a blockage or unsafe debris field.

Rehabilitation actions: Connectivity and infrastructure

  • Remove temporary barriers and restore fish passage between the main channel, refuge pools, anabranches, wetlands and off-channel habitat.
  • Fit permanent pumps and water diversions with effective fish protection screens, bypasses or other approved measures that reduce larval entrainment.
  • Design crossings, culverts, regulators and low flow channels to retain minimum within-channel flow and avoid isolated pools.
  • Avoid rapid changes in water level during the spring and summer breeding period when operating rehabilitated infrastructure.
  • Control weeds, sediment and introduced fish impacts, including carp where the approved management programme addresses them.

Rehabilitation actions: Monitoring and success measures

Breeding temperatures: Approximately 20 to 24 degrees Celsius.

Larval dispersal pattern: Predominantly downstream and mainly overnight in the cited river study.

Movement scale: Most individuals move less than 5 km, so nearby retained habitat should be selected carefully.

  • Monitor water depth, flow, temperature, aquatic vegetation, woody debris, substrate, connectivity and water quality during dry periods and the next breeding season.
  • Use targeted fish surveys to check for adult freshwater catfish, nests, larvae and young fish, with effort concentrated from October to December.
  • Treat successful rehabilitation as stable low flow, retained wet refuge habitat, suitable shallow nest areas, functioning fish passage, reduced pump entrainment and evidence of recruitment where monitoring is required.
  • Record weeds, carp, bank erosion, siltation, fish deaths, screen performance and any loss of aquatic vegetation, and correct failures promptly.
  • Continue monitoring until the approved success measures are met and provide results to the relevant state database and approval authority.

Sources